Salford Lads Club, the local Victorian landmark where the Smiths were photographed in 1986 for the inside cover of their finest album, The Queen Is Dead. In PR terms, the visit was thus a "twofer": a chance for Cameron not only to push the new compassionate Toryism, but to once again yak on about one of his supposedly favourite rock groups and thus remind us that the Conservative party is now groovier than anyone could have imagined.

The plan was for him to have his photo taken in front of the building à la the Smiths, but the local Labour party got wind of the script, and dispatched a pack of activists to foil him. Their placards featured such slogans as "Salford Lads not Eton snobs" and "Oi Dave - Eton Toffs' club is 300 miles that way", and they would not be moved, so Cameron went home without his snap.

Just under a fortnight ago, Salford's MP, Hazel Blears, the doughty secretary of state for communities and local government, recounted the tale at Labour's spring conference. It was, she said, "a story from a great city". When her comrades had got wind of Cameron's plans, they had been "incensed" by the cheek of a Cameron visit to an area that had "80% youth unemployment when the Tories were in power". They had spent "all night" getting ready to protest.

"And on the day," she said, "Cameron was bundled in the back door, and bundled out of the back door. And he never got his photograph! And that night, I couldn't resist it: I sent him a photo of me outside Salford Lad's Club" - and here she laughed like a triumphal drain - "and I wrote, 'Dear Dave, Sorry you didn't get the picture, all the best from Salford.' And when I saw him at the next PMQs [Prime Minister's Questions], he said, 'Hazel - I will get my photograph.' And I said, 'Not on my watch, you won't, Dave.'"

So, there it was: class conflict, the Thatcher legacy and much more besides, all thrashed out to a classic soundtrack - though just to shift the battle somewhere else again, it was only a matter of weeks before Cameron was going on about his fondness for songs of politicised rage written by the young Paul Weller, and Anne McElvoy of the London Evening Standard was talking up his membership of something called "the Jam generation". And so, in the manner of a headache that is slowly getting more painful, the question came up once again: what on earth is going on?

In the two and a bit years since he became Conservative leader - in fact, since he crash-landed in frontline politics circa 2004 - Cameron has taken a leaf out of the Tony Blair manual, and underlined his iconoclastic approach to politics by going on and on about the music he likes. The names he has dropped have included the Nevadan indie-rockers the Killers ("very good and quite energetic"), the Georgia-born songstress Katie Melua ("cheesy", but also "brilliant"), and the snore-inducing sub-Coldplay troupe Snow Patrol ("excellent"). The iPod bought for him in 2005 by his wife Samantha apparently includes music by Johnny Cash, U2, the reggae maestros Sly and Robbie, and the rotund guitar-pop quartet the Magic Numbers. When he was on Desert Island Discs in June 2006, his selections included tunes by Bob Dylan and Pink Floyd.

Most of the above names are either avowedly apolitical, bereft of any substantial content or in thrall to the Bono school of messianic non-politics, but some of the music Cameron affects to like sits in a rather more awkward place. He praises the Smiths for their "brilliant" lyrics; while he was at Eton, he says the music of the Jam "meant a lot"; his initial shortlist for Desert Island Discs included Kirsty MacColl's version of A New England, written by Billy Bragg. At one time or another, all of them were leaders of a subculture that pitted a good deal of British rock music against the party Cameron now leads, but he swats away that incongruity with the same blithe confidence he has used to remarket the Tories as zealous environmentalists and friends of the poor. "I don't see why the left should be the only ones allowed to listen to protest songs," he says, and that seems to be that.

Now, it is obviously nobody's place to tell anyone what they can and cannot listen to, but you have to ask: if the Cameron scenario was replayed on the opposite side of the political spectrum, how weird would that be? There isn't much in the way of pro-Tory popular music (aside from, say, Hello Maggie, sung by the crooner Vince Hill and latter-day Morrisons poster-girl Lulu in 1979 to the tune of Hello Dolly: "Hello, Maggie/Well, hello, Maggie/Now you're really on the road to No 10"), but if there were, would anyone on the left be listening to it? Cameron's fondness for the left-aligned music of yesteryear surely speaks volumes not just about the modern frenzy of political cross-dressing, but also the way we now listen to music. It is as if all those songs have been retrospectively robbed of their political charge and rendered kitsch - just more stuff to be stuck on the great collective playlist, and shuffled beyond any meaning.

When I put in a call to Paul Weller, he mentions Cameron's alleged fondness for his old songs, and expresses a fatalistic puzzlement. "It's like, which bit didn't he get?" he says. "It's strange, but the whole nature of politics has shifted, hasn't it? The stark contrasts of Thatcherism and socialism have gone: you can't really tell who's Brown or Cameron or anyone else. I don't know what Cameron's for or against, really. Even with that div who's running for mayor - Boris Johnson - there's some things he's said that I've found myself agreeing with, like bringing back the Routemaster buses. You sort of think, 'Hang on - I'm agreeing with a Tory twat.'"

When I mention his residual feelings about the long years of Thatcherism, however, out it all comes. "I think they were absolute fucking scum - especially Thatcher, who I think should be shot as a traitor to the people. I still think that, and nothing will ever change my opinion. We're still feeling the effects of what they did to the country now, and probably always will: the whole breakdown of communities, trade unions, the working class - the dismantling of lots of things."

And if I had suggested in 1981 or 82 that there were ardent Tories coming to Jam concerts, what would he have thought? "I'd have been really, really surprised. I think I pretty much nailed where I was at to the mast. But people come to gigs for different reasons: it isn't necessarily about what the person on stage is singing. But at the same time, you do think, 'Well, maybe this'll change their minds.'"

I mention a cue-card that featured in the video for the Jam's 1982 single Town Called Malice, which featured the slogan "If we ain't getting through to you, you obviously ain't listening". "How prophetic that was," he says, drily.

As Weller attests, the 80s were indeed polarised times, during which the implicit political divide embodied by the cold war was firmed up by arguably the most ideologically driven government Britain has ever seen. As Cameron himself has acknowledged, there was "a big gulf between left and right. You were either for CND or Nato, privatisation or state ownership of industry, cutting taxes and setting people free or high rates of marginal tax, for the trade unions or for trade union reform. It seemed to me we made a choice on those sorts of grounds."

We did indeed, and musicians were no exception. The Tories' 18 years of government gave rise to an absolute mountain of anti-Conservative music. Thatcher-hatred, lest we forget, ran so wide and deep that in 1985, the Labour party announced the creation of Red Wedge, the loose artistic-cum-musical project that found some of the era's stars awkwardly standing in close proximity to Neil Kinnock.

By the mid-80s, anti-Tory ire had cohered into a veritable counterculture, which came with pretty clearly defined beliefs. Groups played benefits for such causes as the striking miners, the Sandinista government in Nicaragua, and anyone else laid low by the sudden hegemony of the free-market right. One of my fondest memories of the era is of a long, drunken afternoon listening to bands - including, as I recall, the great 80s annoyance that was Wet Wet Wet - at an event in central Manchester called "Jamming for Jobs" (we waited, but no jobs arrived).

Looking back, it is easy to cringe - and when it comes to a lot of the music, time has inevitably not been kind. Veteran Red Wedger Billy Bragg is still pigeonholed as "a political singer-songwriter", and his oeuvre contains plenty of anti-Tory protest music, but it is his beautifully turned love songs that have weathered best. There is a song by Paul Weller's post-Jam vehicle the Style Council about the Youth Training Scheme, which is better than its subject-matter suggests, but not among their more fondly loved material. For reasons I cannot quite explain, I retain a liking for the ultra-left trio the Redskins, whose stock in trade was spirited soul pastiches with doctrinaire leftwing lyrics (eg "Russia sparked the fires in 1917/First workers' revolution in history"), but I am probably in a minority.

But in among it all, there was some great art. One thinks, for example, of Bragg's soaringly poetic lament for the postwar consensus, Between the Wars, a top 20 hit in 1985; or Town Called Malice, Weller's bone-chilling portrait of a Britain laid waste by the early Thatcherite blitz, and revived as a signifier for post-industrial decline by the makers of the film Billy Elliot. While we are here, we should also go back to the Thatcher period's opening months, and Eton Rifles, in which Weller imagines the class war being fought out at the titular school's gates, and a clarion call going out to what remains of the proletariat: "Sup up your beer, and collect your fags/There's a row going on, down near Slough." Inevitably, the wrong side loses: "All that rugby puts hairs on your chest," sings Weller. "What chance have you got against a tie and a crest?" Cameron says he remembers listening to Eton Rifles ("I was one," he says), which leads you to wonder: did it not cause him and his pals even a faint pang of unease?

When it comes to Cameron's supposedly beloved Smiths, younger readers might want to factor out Morrissey's recent strange views about immigration and his all-round post-Smiths embrace of a crabby kind of small-C conservatism, and think instead about the themes - republicanism, vegetarianism, the rejection of paid employment, you name it - that implicitly put the Smiths at 90 degrees to their time. In January 1986, Morrissey's creative partner Johnny Marr played every date on Red Wedge's opening tour; the whole band performed when the show pitched up in Newcastle. History records that within a week, the Smiths were putting in an appearance at a Liverpool concert titled From Manchester with Love, put on in aid of the 49 Liverpudlian councillors who were facing personal financial ruin thanks to their battles over the thinly veiled cuts policy known as rate-capping (that rock groups were incensed by clashes over local government finance surely speaks volumes about the times).

Streaked through the Smiths' career, more-over, were the kind of anti-Tory pronouncements that the young Cameron presumably ignored.

In the wake of the IRA attack on the 1984 Conservative party conference, for example, Morrissey rather regrettably claimed that "the sorrow of the Brighton bombing is that Thatcher is still alive". By way of pointing up his lack of remorse, his first solo album, Viva Hate, featured a particularly pointed composition entitled Margaret on the Guillotine, which ran thus: "Kind people have a wonderful dream/Margaret on the guillotine/Because people like you/Make me feel so tired/When will you die?" The song has been endlessly mentioned by those who have been querying Cameron's attachment to the Smiths, but to no avail. Just lately, he was once again presented with the words during a Guardian webchat, but batted them away with a glib flourish: "The lyrics - even the ones I disagree with - are great, and often amusing."

A few months after Cameron became Tory leader, I spent a day with Billy Bragg, who had recently prepared for the worst by having his picture taken with Gordon Brown at a Fabian Society event where they were both booked to speak. "I have a waking nightmare where I hear David Cameron saying, 'I really like the Smiths, and Billy Bragg as well,'" he said. "So when the photographer said, 'It'd be great to get a photograph of you and Gordon, I suddenly sat there, thinking, 'Yes! At last! I can send a clear message to the Cameronistas that there's absolutely no chance of them fucking coopting me.

"The ground has shifted severely, from a situation where the leader of the Conservative party more or less formed my whole political outlook, to having a leader of the Conservative party who could have been in the audience at one of the gigs I did in the 1980s," he said. "That really freaks me out."

Based more on a hunch than any kind of certain knowledge, Bragg has a theory that when he, the Smiths and the Redskins played a benefit for the doomed GLC in 1986, Cameron was probably in the audience. If he was, what did he make of what he heard? Perhaps he was not put off by the music's messages because he had the luxury of knowing he was on the winning side. Maybe he had had a few too many Red Stripes to care. Or perhaps he simply didn't get it.

On this score, my favourite story concerns the Cameroonian Tory MP Ed Vaizey, who recently appeared on Michael Portillo's BBC4 Thatcher documentary, The Lady's not for Spurning, talking about the Birmingham-based 80s band the Beat, whom he claims to have "adored", despite being an "ardent Thatcherite". "They had a song called Stand Down Margaret," he marvelled, before telling Portillo he assumed that everyone in Britain admired Mrs Thatcher in much the same awestruck terms as he did, so when it came to the song's target, the penny never really dropped. "I couldn't work out what they had against Princess Margaret," he said. D'oh!

When I speak to him, Vaizey reels off an impressive list of his 80s leftwing favourites. As well as Bragg and his fellow Red Wedgers Madness, he recalls seeing the Redskins ("a fantastic band"), and the words "Fuck Geoffrey Howe" being bellowed from the stage; he still treasures a vinyl copy of their sole album Neither Washington Nor Moscow - strap-lined, in keeping with a Socialist Workers party slogan, "but international socialism".

"I had to lead this double life," he says. "It's hard to explain, really; some of the political messages went over my head. But I thought Thatcher was fantastic, and I was listening to a lot of bands saying she was destroying the country. I suppose I like passion, in politics and music, and these were the passionate bands who were around." Trying to get to the heart of all these contradictions, I suggest that he could blithely ignore their messages because his side of politics had the upper hand. "I think that's a very good way of looking at it," he says. "People could do all this ranting from the stage, but you knew it wasn't going to change the tide of history."

To finish, I read him Weller's "scum" quote, and he takes a deep breath. "That hurts," he says. "The Jam were the band that defined my teenage years. I absolutely adored them."

The New Statesman recently ran a piece by its Tory-watching columnist Tara Hamilton-Miller, in which she surveyed the alleged musical appetites of the rest of the Tory frontbench. Most of them, she said, opted for more politically neutral stuff than their boss: William Hague is rumoured to be a Meat Loaf fan; the shadow immigration minister Damian Green saw Led Zeppelin in concert when he was 16; their schools spokesman Michael Gove pledges allegiance to Scots titans such as Simple Minds, the Proclaimers and the Blue Nile (as well as Wagner); and shadow minister for Scotland, Ben Wallace, appears to rate Aerosmith. There again, the Tory fondness for the music that once soundtracked the anti-Tory resistance of the 80s runs further than the leader's office: in the blog written by Nadine Dorries, the hard-right Tory MP for Mid-Bedfordshire, it was recently claimed that three Conservative parliamentarians were once sufficiently enamoured of the Jam to have seen them play live - Dorries herself, Vaizey, and John "Whitto" Whittingdale, a former shadow culture secretary who once served as a political researcher to Mrs Thatcher.

Cameron, meanwhile, keeps on keeping on. Last week, the Times ran a piece in which he explained a new wheeze whereby people could become an accredited "Friend" of the Conservative party by paying as much or as little as they wanted - a scheme inspired, he said, by Radiohead releasing their latest album In Rainbows online, and encouraging their public to contribute via their now-legendary "honesty box". "Radiohead are one of my favourite bands ... I hope Thom Yorke will forgive me for ripping off his idea," he wrote, and the mind once again boggled. You might think of Radiohead as the merchants of a dissenting, anticonformist worldview that has led their singer to public support for CND - but they may yet go down in history as the band who inspired a new model of Conservative party membership.

So what is left? How long before Cameron or one of his allies carries off a gung-ho raid into another place they probably do not belong and admits to Sunday afternoons spent happily watching Ken Loach DVDs? By way of cold comfort, anyone feeling troubled is hereby advised to go back to an aforementioned Weller song, and righteously bellow the lyric in the way we used to in the dread days of Tory misrule: "Hello, hooray, I'd prefer the plague/To the Eton rifles".