Former Prime Minister Sir John Major hit out at the way Labour used accusations of "sleaze" to blacken the reputation of the Conservative Government in the 1990s.
Sir John compared the tactics adopted by Tony Blair - then leader of the Opposition - to the McCarthyite witchhunts against communist sympathisers in the United States in the 1950s.
While he acknowledged that there had been individuals in the Tory Party who "misbehaved" in the 1990s, he said that under Labour the problems of "sleaze" had become "systemic".
"What they did at the time was absolutely unscrupulous," Sir John told BBC1's The Andrew Marr Show.
"Lots of people misbehaved in the 1980s and 1990s, but they were all individuals. It was never institutional. It was never related specifically to the Conservative Party or to the Conservative government.
"What happened in the 1990s, there was a deliberate attempt to portray the Conservative Party as an institution - it was almost McCarthyite frankly - as though it were sleazy and it wasn't.
"The distinction is that sleaze has seemed to be systemic since 1997."
Sir John has spoken little about his feelings about what happened in the 1997 general election since losing power, but his comments suggest that he continues to nurse a deep sense of grievance.
The Conservatives were hit particularly hard by the so-called "cash-for-questions" scandal, with the disclosure that Harrods store boss Mohammed al Fayed had been paying Tory MPs to ask questions for him in Parliament.
Mr Blair has recently expressed his regret at the way Labour used the accusations of sleaze against the Tories, acknowledging that all political parties were basically honest.
