Peter Hain installed himself as Tony Blair's chief political bodyguard yesterday, dismissing claims that the Prime Minister should step aside as 'fantasy'.
Mr Blair will seek to reassert his authority today when he completes his reshuffle amid mounting calls for him to go.
Former Cabinet ministers Frank Dobson and Robin Cook feature on the roll-call of backbenchers calling for him to stand down.
Mr Blair will try to use the remaining reshuffle to shake off the 'lame duck' accusations that have followed the election.
The reduction in Labour's majority from 161 to 67 have sparked calls for him not to stay on for the full final term.
Mr Hain was the loudest of the Blair brigade voicing their support yesterday. He was joined in the counter-attack by David Blunkett, newly restored to the Government's top ranks, who branded critics 'self indulgent'.
Mr Hain, who has a new role in Cabinet as Northern Ireland Secretary alongside the equivalent role in Wales, said, 'People suddenly want to have his head on a plate within hours of winning this historic third term of office and consigning the Tories to a terrible result and a third successive defeat.
'The idea that would be welcomed by the public I just think is fantasy.'
Mr Hain was also keen to defend his own ability to combine both roles, at a time when the Government is making resolving the Irish peace problem a 'priority' and there is a White Paper due on more powers for the Welsh Assembly. He described claims he would not have time to do either job sufficiently as 'poppycock'.
Northern Irish politicians have accused Mr Blair of downgrading the Irish post by not making it full time. Meanwhile, Mr Blunkett acknowledge a need to 'build confidence' behind the Prime Minister following the attacks on his integrity during the election.
However, those saying the PM should go after his majority was slashed were trying to 'snatch defeat from the jaws of victory', the new Work and Pensions Secretary said.
Labour media supremo Alastair Campbell insisted Mr Blair was 'absolutely right' to serve a full third term as he promised.
'Those who write him off today are doing so very, very prematurely,' he warned.
But former Health Secretary Frank Dobson said, 'He was an enormous liability in this general election.
'If he had not been leader I doubt whether we would have lost a seat. We would probably have gained some.'
Robin Cook, who quit the Cabinet over Iraq, said he should be respected for making Labour 'the natural party of government' but should go before next spring's council elections.
'The question Tony Blair should be reflecting on this weekend is ... whether now might be a better time to let a new leader in who could then achieve the unity we need if we are going to go forward.'
Dave Prentis, leader of the giant Unison union, also suggested time was running out for Mr Blair.
'The reality is that we need a new leader well in advance of the next election,' he said.
Former minister Frank Field, a regular critic of the Government, said, 'The Blair factor went a long time ago.'
He was unimpressed by the changes to the Cabinet, which he said lacked 'substantial people'.
'You'd think you were doing a cabinet for Toy Town,' he said.
There are 'two gangs' running the party, according to Mr Field.
'We are now becoming so fed up with this gang warfare in the Labour Party that there is a tendency if Mr Blair can last long enough ... that we might look for somebody who is not part of one of those gangs,' he added.
Mr Campbell also defended the PM's reshuffle amid signs of a new power struggle with Gordon Brown.
The Chancellor is said to be resisting the appointment of No 10 education adviser Andrew Adonis as Schools minister.
Education Secretary Ruth Kelly was rumoured to be heading back to the Treasury as Chief Secretary.
Ms Kelly has remained in her post but it was not clear whether Mr Adonis would be made a peer and become her deputy when the rest of the new government is unveiled.
John Denham, who resigned from the Home Office over Iraq, and Beverley Hughes, who quit as Immigration minister over an Eastern European visa scam, are tipped to return.
Culture Secretary Tessa Jowell was expected to be made Cabinet Office Minister for Women as consolation for missing out on the top job at health.