Labour Chairman John Reid has been named as the new Leader of the House of Commons in a mini government reshuffle.
Reid is moving again in the latest reshuffle
Dr Reid, until now Labour chairman, replaces Robin Cook, who resigned almost three weeks ago saying he could not support the government's stance over war with Iraq.
The changes also see Pensions Minister Ian McCartney succeed Dr Reid as Labour Chairman.
He is seen as a man the prime minister turns to when he has a problem he wants to solve
The appointment of former Northern Ireland Secretary Dr Reid, shows that Tony Blair wants one of his cabinet heavyweights playing a key Commons role after the recent record rebellions.
He is seen as a man the prime minister turns to when he has a problem he wants to solve.
Dr Reid only moved to become Labour Chairman in October last year in the reshuffle which followed Education Secretary Estelle Morris' resignation.
Mr McCartney has previously been a minister at the Cabinet Office and the Department of Trade and Industry.
The prime minister has used him as a key link between the government, trade unions and the Labour Party, where he is a popular figure.
The new Labour chairman has been a key figure within the party because of his links with the unions and Labour's grassroots
As he took up his new post, Mr McCartney told BBC Radio 4's World At One his job was to re-enthuse party members.
He had long campaigned for party members to have a bigger say, he said.
"My role's to be the voice for party members in government," added Mr McCartney, who denied he would need to sell unpopular policies to party members.
Trade unions, including TUC general secretary Brendan Barber, have welcomed his promotion.
Former Labour minister Peter Kilfoyle said Mr McCartney was very affable but he offered no magical solution to the key problem.
"It is not the personalities, it's the policies they are trying to sell," he said.
Robin Cook was the first minister to resign over Iraq
Former Labour whip Graham Allen, who helped organise rebels on the Iraq votes, said the parliamentary "prison" would wait to see if Dr Reid proved a liberator or just a new governor.
He told BBC News Online: "I hope that the new leader of the House will adopt a strategy of seeing Parliament as a partner with government, rather than as a problem to be contained."
Asked about Mr McCartney's promotion, Mr Allen added: "I hope that Ian sees himself and is allowed to play his role as Labour's influence within the cabinet so that the party is reunited with its government and not merely managed as an irritant."
Liberal Democrat spokesman Paul Tyler said MPs from all parties would be dismayed at Dr Reid's appointment.
"Dr Reid will have to make the mental switch from imposing the will of a party dictatorship to promoting the merits of parliamentary democracy," said Mr Tyler.
"He has a reputation as 'King of the Control Freaks' to live down."
'Paying the price?'
Conservative chairman Theresa May suggested Dr Reid was being moved because he had only managed to find Labour candidates for 65% of the council seats up for grabs in May.
"It seems that Mr Reid is paying for his failures and his removal from the post is a damming indictment of the Labour Party's performance at both local and national level," she said.
But Tony Wright, chairman of the Commons public administration select committee, said Mr McCartney and Dr Reid would help "bring everyone on board" and get Labour members feeling involved.
The Home Office minister in charge of homeland defence, John Denham, and Health Minister Lord Hunt also quit their government posts over Iraq.
But neither of them is likely to be replaced until next week at the earliest.
There is speculation that the prime minister might wait until the war is finished before giving Mr Denham back his old job.