Former Prime Minister Sir John Major has accused Labour of presiding over "systemic sleaze" during its 10 years in government.
Sir John said the government had become "institutionally careless", citing as examples the Bernie Ecclestone affair and the David Abrahams funding row.
He said Tories had misbehaved when he was PM as individuals not members of government.
Labour accused Sir John of "backward-looking mud-slinging".
Whiter than white
Speaking on BBC One's Andrew Marr Show, Sir John also accused Labour of carrying out a "McCarthyite" campaign against his Conservative government.
Sir John said Tony Blair should apologise for what he had said about the Conservatives in the 1990s, and that he had behaved in an "unscrupulous" way.
People would laugh if the government now claimed to be "whiter than white, purer than pure," he said.
He acknowledged that "lots of people misbehaved" when he was prime minister, but said they did so as individuals rather than members of the government. It was not institutional sleaze, he said.
Sir John warned that the good economy that Labour inherited from the Conservatives "is now beginning to unravel".
He blamed government policies on pensions and too many taxes for a drop in competitiveness and productivity.
"The economy is running into serious difficulties," he said.
He added that Gordon Brown's decision to sell much of Britain's gold reserves in 1999 had lost the economy billions of pounds.
And he predicted that losses to the taxpayer incurred by the Treasury's attempts to bail out the ailing Northern Rock bank would exceed those created by Black Wednesday in 1992.
"I hope this will stop Gordon Brown talking about 10 successful years, " he said.
Labour MP Graham Allen said: "Sadly Sir John Major's attempt to rewrite history will only serve to remind us that, on his watch, there were countless Tory funding scandals in the 90s, including Neil Hamilton, Jonathan Aitken and Azil Nadir.
"During his tenure donations were not all declared and foreign donations were commonplace. It took a Labour government to end those scandals and introduce legislation to bring greater transparency to party funding."