Tony Blair is "history" and his supporters must bury the hatchet with Gordon Brown and move on, a former cabinet minister has declared.
Stephen Byers has appealed for an end to "old battles"
Stephen Byers said everyone seeking a Labour election victory must throw their weight behind the prime minister.
Writing in the Observer, he also warns 2008 will be Labour's most challenging year since its 1992 election defeat.
The appeal comes after an embattled few months for Mr Brown and underlines Labour nerves about a Tory resurgence.
But the olive branch also comes with a warning that Mr Brown will need a broader appeal if Labour is to see off the Conservative threat.
Mr Byers, the MP for North Tyneside and a prominent Blair supporter, previously called for a high-profile challenger to take on Mr Brown in the race to succeed Tony Blair.
He also indicated he did not expect Labour to "slavishly" follow Mr Brown's agenda if he became leader.
But he now writes: "Tony Blair is history. He is the political past and will not be part of the future of domestic politics in our country.
"2008 will be a tough year. With Tony Blair gone from domestic politics, the task of leading Labour to victory falls to Gordon Brown.
"It is the responsibility of all of us who want to see a fourth election victory to give him our support."
According to the Observer, the article was written in consultation with Blairite former cabinet allies, Alan Milburn and Charles Clarke.
Mr Byers stresses that the former PM - now a Middle East peace envoy - expects total support for his successor, noting his publicly stated intention not to be "a back-seat driver".
"This means that each issue Labour has to deal with no longer has to be seen through the Blair-Brown prism," he argues.
"Such a new freedom places a responsibility on all of us to resist fighting old battles or revisiting past divisions."
But he also warns the prime minister - who faces his first key electoral test in May's local elections - that motivating Labour's core vote is not enough.
"We also have to appeal to the promiscuous voter by demonstrating that we can be the party of aspiration and ambition as well as social justice and fairness."