Dominic Lawson: The delusions and smears that make some voters ashamed to admit they are Tories

While he is enjoying the sort of adulation more normally accorded to rock musicians, perhaps David Cameron could rename the Conservative Party in the manner of a well-known rock star: The Party Formerly Known As Nasty.

That, after all, has been his mission, described by his own advisers as "the decontamination strategy". It is a strategy which continues to irritate many Conservatives of an earlier generation. As Maurice Saatchi, one of the principal architects of its electoral successes under Margaret Thatcher recently observed of Mr Cameron's approach: "Nicey-nicey has not led to more affection for the Conservative Party."

Most recent opinion polls have borne out Lord Saatchi's claim – although we can expect the traditional post-conference bounce to offer some support to the arguments of the nouvelle regime. There is, at the heart of this tussle, a simple truth: in this country it is widely thought that to identify with the Left marks you down as someone motivated by high ideals of altruism, while to vote for the traditional party of the Right suggests that you are acting merely out of self-interest.

This perception allows politicians of the centre-left to get away with remarks that would never be tolerated when uttered by a Conservative. Imagine, for example, if a Conservative leader had made the pledge uttered by Gordon Brown at the recent Labour Party conference, that he would guarantee "British jobs for British workers". It would be denounced as "racist" or even as "stealing the policies of the British National Party".

Sometimes this attitude makes it impossible for even quite intelligent people to believe that the Conservative Party has done any good, ever, in its entire history. One of this newspaper's columnists wrote of Cameron's attempt to fumigate the Tories' reputation: "The Conservative Party has had many images, but retains an unchanging purpose, which is to represent the minority of wealthy people who control society. That's why they opposed the abolition of Slavery and the Factory Acts."

The author had clearly found it difficult to come to terms with the fact that William Wilberforce was a Tory, as was the 7th Earl of Shaftesbury, the driving force behind the Factory Acts of 1847 and 1853.

At its worst, this attitude extends to regarding all Tories as wicked – a view most memorably expressed by Aneurin Bevan, who declared that they were "lower than vermin". It is obviously true that individual Conservative politicians have, over the years, been guilty of appalling moral lapses. Jonathan Aitken and Jeffrey Archer spring to mind, both of whom perjured themselves in an effort to win substantial libel damages. Their eventual unmasking – and the prison sentences that followed – did more than anything else to earn the Conservatives the unwanted soubriquet: "The party of sleaze."

In fact Aneurin Bevan, the architect of the National Health Service, was guilty of exactly the same form of corruption. Fifty years ago, a young journalist on The Spectator, Jenny Nicholson, wrote a satirical piece about the 23rd annual congress of the Italian Socialist Party, headlined "Death in Venice".

The piece described how a British Labour Party delegation consisting of Bevan, Richard Crossman and Morgan Phillips "puzzled the Italians by their capacity to fill themselves like tanks with whiskey and coffee ... Although the Italians were never sure the British delegation were sober they always attributed to them an immense political acumen."

The three Labour men issued a libel writ against The Spectator, then owned and edited by the future Conservative Cabinet Minister Ian Gilmour – who died last week. After a trial, they won what was then an immense sum in damages and costs. Jenny Nicholson – whose career was blighted by this – had talked to waiters and other delegates, so Gilmour stood by her, convinced that her story was true. It was. Richard Crossman's diaries revealed that the story was accurate and in 1978 Brian Inglis on What the Papers Say reported that Crossman had told him a few days after the case that they had committed perjury.

What made this all the more disgusting was that in the run-up to the trial a nervous Gilmour had offered to publish an apology and pay the claimants' legal costs. As he wrote subsequently: "We proceeded under the naïve delusion that three leading Labour Party figures would not want to commit perjury for money. But that was just what they did want to do. They were greedy." According to one of Bevan's biographers, John Campbell, "Bevan seems to have thought that ... the opportunity to win some damages was too good to miss."

This does not discredit Bevan's political achievement in setting up the NHS – although his own venality seemed to have given him an insight in how to win doctors over to the idea of nationalisation: "I stuffed their mouths with gold".

Even had Bevan experienced the just deserts meted out to Aitken and Archer – a trial for perjury followed by prison – I suspect that there might still be a statue of him in the centre of Cardiff. It would doubtless have been argued that Bevan's noble ideals as a socialist meant that his personal corruption was entirely forgiveable – and besides, what fun to steal loads of money from a rich Conservative like Gilmour! The fact that Gilmour used The Spectator to campaign for the abolition of the death penalty and the legalisation of homosexuality would be irrelevant: he was a Tory, ergo he was ineligible for public sympathy.

Perhaps Gordon Brown's public embrace of Margaret Thatcher, as much as David Cameron's formidable charm offensive, might help to eradicate the stigma – at least among much of the middle classes – of being labelled a Tory. Strangely enough, however, it is the very existence of that stigma which might provide Mr Cameron with some encouragement even in the recent opinion polls.

As Professor John Curtice observed in yesterday's Independent, "the polls have consistently overestimated Labour's strength at recent elections". Why should this be? It is almost certainly because many people feel uneasy about admitting their intention to vote Conservative.

At recent general elections, the Labour margin of victory has been so great that the pollsters' inability to pick up the true level of support for the Conservatives has not mattered. If the next general election is much closer then this factor could become very significant – as it was in 1992, when John Major won against the odds.

Perhaps David Cameron should actually be hoping that he has not succeeded in "decontaminating the Tory brand" – and rely on a hidden wave of support from Conservative voters who, for no very good reason, feel that they can confess their own opinions, like penitent Catholics, only in the dark obscurity of the ballot box.

d.lawson@independent.co.uk