The first salvo was fired by the former head of the UN weapons inspectors, Hans Blix, who launched a blistering attack on Blair's use of intelligence data over weapons of mass destruction.
Hours later, political heavyweight Clare Short - a former cabinet minister - called on Blair to resign.
In a highly critical report, Hans Blix questioned Blair's claims that Saddam Hussein could deploy weapons of mass destruction in 45 minutes.
"It seems to me highly unlikely that there were any means of delivering biological or chemical weapons within 45 minutes," he said.
The highly-respected inspector also dismissed the British government’s September dossier as “pretty far off the mark” in an article published in the London-based Independent on Sunday.
Despite retiring last month as head of the UN weapons inspectorate, Blix has continued to call for UN inspectors to be allowed to return to Iraq.
The former chief inspector added international inspectors from the UN would bring "greater credibility" to the continuing American search for the elusive WMDs.
UN inspectors left Iraq in March as American and British forces prepared to invade and occupy Iraq.
Calls for their reinstatement have been denied, with the US occupation authorities preferring instead to set up their own body - the Iraq Survey Group.
Call for resignation
Clare Short, the cabinet minister who resigned over Iraq, initially brought high profile attention to the dubious 45 minute claim.
Short on Blair: He sees himself
as a higher mortal
The ex-minister called on Blair to step down before things get "even nastier" in a televised interview on Sunday.
Speaking on GMTV's Sunday Programme, Clare Short said the degree of trust in the country had gone down remarkably.
Short added that, in the past, party leaders tended to hang on while their popularity was falling and warned of "a big nasty split" that would damage the party, making it unattractive to the electorate if Blair stayed.
The former International Development Secretary also accused Blair of leading Britain into the conflict on the basis of "half truths" and "slight deceptions".
One of Short’s most stinging attacks on Blair accused the prime minister as seeing himself as "a kind of higher mortal than the rest of us" when he was taking decisions on Iraq.
"I'm sure he's convinced that what he did was right but I'm also sure that he fooled the country in a series of ways in a way that's intolerable when it's a matter of war and peace and human beings' lives and the future of a country," she said.