The Conservative leader has launched a fierce attack on Labour's record in government, saying a turning point in British politics has been reached.

In a speech on Monday night to the Conservative Party Winter Ball, Iain Duncan Smith accused Tony Blair of failing to honour is pledge to be "purer than pure" and of corrupting politics while blaming everyone but himself.

"We come together at what I think is a turning point in British politics. It is now becoming obvious to everyone that Tony Blair doesn't know whether he's coming or going," said the Conservative leader.

He listed a series of sleaze allegations to hit Labour, including the Bernie Ecclestone donation, Peter Mandelson's "unique approach" to the right to buy and passports, and letters to foreign leaders to smooth the path of Labour-supporting contractors.

"Is that what Tony Blair meant by 'purer than purer'?" he asked.

"We now have spin-doctors trying to bury bad news under the rubble of the World Trade Centre, and the entire government machine goes to war against a 94-year-old women for complaining about her hospital treatment."

And he said the government was attempting to lay the blame for public cynicism about politics on anyone but itself.

"Our politics has been corrupted. It has descended into incompetence and cynicism. And who is to blame for it all? Apparently we are.

"It's the forces of conservatism, it's the public servants who leave scars on the prime minister's back, it's the 'wreckers' who are at fault. The last person to use language like this was Stalin in 1930s, but Tony Blair, unlike Stalin, can't make the trains run on time."