Political history is being made before our eyes. Last week we saw a House of Commons Speaker being forced out of office for the first time in more than 300 years. And then two peers, Lords Truscott and Taylor, were suspended from the House of Lords as a consequence of The Sunday Times’s cash for amendments exposé. Peers have not been suspended from the Lords since the 17th century.

The light shone by newspapers on the behaviour of Britain’s political class has fuelled this turmoil. Successive investigations by The Sunday Times, from cash for questions in the mid-1990s, through cash for honours and then cash for amendments more recently, have exposed widespread wrongdoing in high places.

Now The Daily Telegraph, with its thorough analysis of the unexpurgated expenses claims of MPs, has provoked a mood of public anger on an unprecedented scale. Not only has the pomposity of our politicians been pricked but many of them have been shown to be unfit for public office.

Not for the first time Rowan Williams, the Archbishop of Canterbury, manages to strike the wrong note. Writing yesterday, he warned that “the systematic humiliation of politicians” threatened to undermine Britain’s democracy. So it does, but only because it has shone a light on the dishonesty and greed of our elected and unelected leaders.

There can be only one logical outcome from this. It is not always the case that the interests of the country and those of the political system coincide. On this occasion they clearly do. Parliament needs the cleansing effect of an early general election more urgently than it has ever done before. As many as half of the current crop of MPs may disappear in such an election, through a combination of deselections, voluntary retirements and the substantial loss of seats that the inevitable big swing away from Labour will bring.

The next House of Commons will look very different. That does not mean depriving it of all its characters; a parliament full of ascetics and party apparatchiks would be dull and uninspiring. But many of the “characters” exposed by the expenses scandal have contributed little to Britain’s political life. David Cameron should be grateful for the opportunity to clear out the Tory squirearchy, relics of a best-forgotten political age. He has the chance to reshape the party into a modernising force, with far more women and MPs from ethnic minorities.

The process cannot start immediately. A summer election would be too soon for voters to be able to judge fairly whether or not their MPs have behaved well. Public anger is too raw, threatening to produce a distorted election outcome that we would repent at leisure. We do not want a character-free Commons but neither do we want one full of oddballs, elected simply because they were not from the main parties.

None of this, however, argues against the overwhelming case for an autumn election. Parliament needs it, and so does the country. Last week both the International Monetary Fund and Standard & Poor’s, a credit-ratings agency, warned that Britain’s public finances needed further drastic surgery. If not, then at the very least taxpayers will have to pay a great deal more for funding the government’s enormous borrowing. At worst, there could be a full-blown fiscal crisis.

Both the IMF and S&P recognise that such action is unlikely this side of an election. The Treasury’s twice-yearly review of government spending, planned for this summer, has been scrapped. Labour argues that these things take time, that the economy could start recovering by the end of the year.

This government does not deserve more time, however. It is clinging desperately to power, having lost any sense of direction. The alternative to an autumn election is months of damaging drift. The deep wounds of the expenses scandal will fester if voters are not given the chance to register their views. Above all, an early election will give us the opportunity for a new start. Rarely have we needed it more.