The charge of incompetence is the deadliest that one can level at a government. In a memorable exchange with Gordon Brown in 2007 following a Labour Party funding scandal, David Cameron declared: “We have had 155 days of this gov­ernment. We’ve had disaster after disaster. A run on a bank, half the country’s details lost in the post and now this . . . Aren’t people rightly asking, ‘Is this man simply not cut out for the job?’” Now, the Prime Minister has suffered his own funding scandal – they are a tedious and periodic feature of British politics – and it is the suitability of Mr Cameron and his senior colleagues for their roles that is in doubt. The cash-for-access affair came after rows over the ill-explained “granny tax” and “pasty tax” and was followed by a fuel crisis provoked by the government for political purposes.

Adding to this toxic brew is the accusation that the Con­servative leadership has little understanding of the lives of voters. After the interregnum of the Thatcher and Major years, the feeling once more is that the Conservative Party has been recaptured by the trust-fund classes.

Mr Cameron, like most of his ministers (and indeed the high command of the Liberal Democrats), is a son of privilege. As his former rival for the Conservative leadership David Davis observed of the cabinet: “They [the voters] look at the front bench. They see them all very well turned out, well fed; they look like they’re in a completely different world.”

Yet the decline in support for Mr Cameron – his approval rating is at a record low of -27 – has not been accompaniedby a rise in enthusiasm for Ed Miliband or Nick Clegg. The three main party leaders are collectively the least popular in the history of polling. However, George Galloway’s triumph in the Bradford West by-election is unlikely to be replicated elsewhere in the country – the maverick Respect MP is aformidable and articulate campaigner, with a crude, populistappeal that few of his comrades on the far left can match.

But the decision by six in ten voters in Bradford West to support parties other than the main three reflected a profound and widely shared distrust of the political establishment. The Liberal Democrats lost their deposit and the Conservatives’ share of the vote collapsed from 31.1 per cent to 8.4 per cent. The gulf between the political class and those they ostensibly represent has perhaps never been wider.

At the root of the problem is the “professionalisation” of politics, which has left ever fewer MPs with what Denis Healey called a “hinterland” – knowledge and experience of life beyond Westminster, Whitehall and the think tanks. An increasing number studied at Oxford or Cambridge (as 30 per cent of all present MPs did) and then worked as a special adviser to an MP before being parachuted into a safe seat. Research by the Smith Institute shows that, of the 2010 intake, 24 per cent were former political advisers, up from just 3 per cent in 1979.

The long decline of trade unionism – from 13.5 million members in 1979 to 6.5 million today – has deprived working-class activists of a route into national politics, and a dearth of female and ethnic-minority MPs in the cabinet confirms the impression that politics is a game for white,upper-middle-class men.

The coalition’s policies will exacerbate the problem. Its plan to cut the number of MPs from 650 to 600 will slow progress to equality by reducing the number of seats available to new women and ethnic-minority candidates. Until MPs of all parties demonstrate a willingness to reform our unrepresentative democracy, they will neither have nor deserve the trust of the voters and there will be no grand transformation of the economics and politics of the British state.