David Miliband has called on his supporters not to allow his leadership rivalry with brother Ed to degenerate into the kind of infighting which disfigured Labour during the Blair/Brown era.
Making his first appearance on the conference stage in Manchester since losing out to his brother in the race to succeed Gordon Brown, David hailed Ed as "a great new leader" for Labour and urged the party to unite behind him.
In a clear warning against the dangers of internal warfare within the party, he told the conference: "No more cliques, no more factions, no more soap opera - one united Labour Party taking on a divided Government."
However, David gave no indication of whether he wants to be part of his brother's frontbench team in the new shadow cabinet.
With elections to the shadow cabinet concluding on October 7, Ed Miliband indicated that he will not make any announcement on posts in his top team until next week at the earliest, and said that David should be given time to "make his own decision about the best thing for him".
The former foreign secretary has until 5pm on Wednesday to decide whether to put forward his name for the shadow cabinet elections, which are expected to involve 50 or more MPs chasing 19 slots around Mr Miliband's top table.
The Manchester gathering has been dominated by speculation over whether David will walk away from front-line politics following the bitter disappointment of losing the race to succeed Gordon Brown which he had long been favourite to win.
He acknowledged that his defeat at Ed's hands by a margin of just 1.3 per cent had caught him off guard, telling the conference that he had written a victory speech for Saturday and many drafts of what would have been his first leader's speech on Wednesday.
But he told delegates, who welcomed him on stage with warm and extended applause, not to be concerned about the impact of defeat on him, assuring them: "Don't worry, I will be fine."
While he had been "100 per cent committed" to fighting for the leadership, he had gone into the contest "reconciled to the prospect" that he might lose, he said.
In a speech added to the conference schedule at the last minute, David Miliband said he was "incredibly honoured and humbled" by the support he had received.
But he told supporters: "We have a great new leader and we all have to get behind him.
"I am really, really, really proud. I am so proud of my campaign. I am so proud of my party. But above all I am incredibly proud of my brother. I see Ed as a special person to me. Now he is a special person to you and our job is to make him a special person for all the British people."
Ed dismissed reports of tensions with his brother: "There is no psycho-drama. David and I have been extremely close during this contest, before the contest and after this contest, and the graciousness he has shown since Saturday speaks volumes about him as a person.
"He will make his own decision. I will make my decision about the shadow cabinet, but these aren't decisions for this week, they are decisions for next week and the week after."