Deputy Prime Minister John Prescott’s admission of an extra-marital affair followed a blunder which allowed the release of 1,023 convicted foreign nationals from British jails without being considered for deportation.
And to add to the government's woes, Patricia Hewitt, the health secretary, was booed, jeered and slow-handclapped during her speech to the Royal College of Nursing in which delegates shouted for her to stand down.
In the end, she was forced to abandon her televised speech because of the disruptions.
Mr Blair has been under pressure since last month when Labour said it had received nearly STG14 million ($A33.68 million) in loans from 12 businessmen, some of whom were later nominated for seats in the unelected upper house of parliament.
Mr Prescott, 67, spared Mr Blair any prolonged agony when he immediately admitted to tabloid revelations that he had cheated on his wife by having a two-year affair with a civil servant 24 years his junior.
"I did have a relationship (with secretary Tracey Temple) which I regret. It ended some time ago. I have discussed this fully with my wife Pauline who is devastated by the news," Mr Prescott told the Daily Mirror newspaper.
A spokesman for Mr Blair declined to comment on the revelation, saying only: "It is a private matter."
Prescott gaffs
Mr Prescott, a veteran political heavyweight, is notorious for his gruff and sometimes gaff-prone style.
He made headlines during Britain's 2001 election campaign when he punched an egg-throwing protester.
But his current indiscretion was liable to pale quickly in comparison to the more politically-charged flap about foreign prisoners.
They included three murderers, nine rapists, five child molesters and 20 drug smugglers, and more than 900 of them remain unaccounted for –- calling into question Mr Blair's long-held commitment to be "tough on crime".
Around 160 of them were subject to court orders specifically recommending their removal from Britain.
Mr Blair said on Wednesday: "I fully accept and regret that until recently the system for identifying and, where possible, deporting foreign nationals, who have served sentences in United Kingdom jails, has been seriously and fundamentally at fault."
Local elections
The debacle comes the week before Mr Blair's Labour Party contests local elections -- the prime minister's first test at the ballot box since he won a third term in office last May.
According to one poll published this week, the Labour party is less popular now than at any point in the past 19 years.
The Home Office's failure over foreign prisoners is expected to play into the hands of the opposition Conservative Party and the fringe far-right British National Party (BNP) in the May 4 ballot.
The BNP is campaigning on an anti-immigration ticket.
The government department has admitted it has no idea where most of the ex-convicts now are.
It has also said it does not know how many, if any, have reoffended since their release.
Home Office head Charles Clarke, a close ally of Mr Blair, offered to resign over the bungle, but Mr Blair asked him to stay on.
The government has blamed the administrative error on a lack of communication between the prison service and immigration authorities. Mr Clarke has described it as "a shocking state of affairs" and vowed to remedy it.
Blair under fire
If Labour suffers big losses next Thursday, it could hasten the day that Mr Blair decides on his pledge to stand down sometime during his third term to make way for his more popular finance minister Gordon Brown.
Mr Blair is already under fire over a number of other burning issues, from layoffs in the cash-strapped, free-care-for-all National Health Service to a the furore over the nomination of rich Labour supporters to parliament's unelected upper House of Lords after election-year loans that were not declared.
Police are investigating the latter case, with detectives refusing to rule out a full-fledged corruption inquiry.
Also in hot water has been Culture Secretary Tessa Jowell, like Mr Clarke a loyal Blairite, who has separated from her lawyer husband after allegations of bribery against him involving former Italian prime minister Silvio Berlusconi.