London, Dec. 12 (Reuters): The British minister under investigation for allegedly fast-tracking a visa for a former lover?s nanny was at the centre of a new political storm today over slurs on his government colleagues.

Opponents of Prime Minister Tony Blair said candid criticism of fellow top-level ministers by home secretary David Blunkett in a biography could precipitate Blunkett?s downfall.

Blunkett, who is blind, oversees Blair?s anti-terrorism and security policies ? central planks of his reelection bid.

His resignation would be a blow to Blair, sparking a cabinet reshuffle with just months before an expected vote in May.

Government figures rallied around Blunkett following media reports he speeded up a visa for the nanny of US-born Kimberly Quinn, a married woman with whom he had a three-year affair.

But his criticism of his colleagues has stretched loyalties and kept the media spotlight on Blunkett as he braces for the findings of an inquiry into the visa row, expected out shortly.

?He hasn?t helped his own cause,? Opposition Conservative Party parliamentarian Tim Yeo said on Sky News. ?I think these comments in the book will damage his chances of survival.?

In book extracts published in past days, Blunkett said foreign secretary Jack Straw had handed over the home office to him in a ?giant mess?. He also praised Michael Howard, now leader of the Conservatives, for his tenure as home secretary in the 1990s.

He said Chancellor of the Exchequer Gordon Brown ?had been throwing his weight?, accused one minister of being ?weak? and another of not thinking strategically.

Health secretary John Reid said today the comments had caused a ?degree of embarrassment? but were not a big issue. ?I think obviously it?s not entirely helpful that it comes out at this stage,? he told Sky News. ?We?re all big boys and girls. We can take it.?

He said Blunkett had strong support within cabinet.

Polls show Blair is poised to win a third term but Blunkett?s comments and the visa row give his opponents much-needed ammunition. Blair promised ?purer than pure? government when he came to power in 1997.

Critics question Blunkett?s ability to focus on his job while engaged in a legal battle to ensure access to a son Quinn bore two years ago.