Relations between Peter Mandelson and the prime minister have been strained since Mr Mandelson backed Tony Blair to be Labour leader in 1994.
The two have fallen out in private and public
Their on-off relationship has mostly been carried out in private or through anonymous briefings in the press.
Here is what Mr Mandelson has said about their feud in public:
AS EU TRADE COMMISSIONER, NOVEMBER 2004
"It would be a good idea if many of Gordon's supporters didn't take their fight with me onto the European stage.
There is no benefit at all for us taking these parochial fights and these past divisions onto the European stage.
So I hope that we can draw a line and we can all move on."
ON THE BLAIR / BROWN 'DEAL', SEPTEMBER 2006
"Within the party, or more strictly within the New Labour family, there has been a fissure really from the word go.
And the reason for that is that Gordon thought that he could and should have been leader in 1994.
He believed that he should have succeeded John Smith and he's never fully reconciled himself to not doing so.
For all the regrets that he might have had that he was not leader and prime minister himself during this period, I think he does recognise Tony Blair's qualities and I think that is entirely reciprocated from Tony Blair to Gordon Brown.
Should Gordon Brown be the one to succeed him he will want Gordon Brown to succeed as leader and as prime minister and he will want him to be re-elected and he will work for that.
There's no sense in Tony's mind '...you know, I was the golden years and now the fallow times must follow'. He doesn't feel like that at all.
I do think he [Gordon] is a winner. He has got a very solid body of beliefs. There is nothing surface or superficial about Gordon Brown. He has real depth and I think people want to see that in their nation's leader.
The chancellor might have all sorts of flaws but his inner strength as a politician came through [in his conference speech].
What I heard was a coming to terms with the need to change to a more collaborative and unifying style if he became leader of the party."
ON BROWN FACING A LEADERSHIP CONTEST, MARCH 2007
"Do I think the party would benefit from a contest? Yes I do.
Do I think whoever was elected would benefit from having a contest? Certainly. I think the prospect of a coronation is off-putting to the public.
That [if he would like Brown to become PM] depends on the choice doesn't it? I mean you're presented with a choice, a number of individuals and you say who will be best.
I don't know whether this is going to come as a disappointment to him, but he can't actually fire me [as EU trade commissioner]."
ON BROWN'S CONFERENCE SPEECH, SEPTEMBER 2007
"We know from his speech yesterday much more clearly what a Gordon Brown government would do. We know the 'what' but what he's got to do now is set out the 'how' and that is the challenge for him.
He is going to be asked more questions, not fewer, about what he said yesterday. If they have got answers to all those questions then we are ready to fight an early election. If they have not then we are going to have to take a little longer.
The expectation was that under Gordon Brown the party would lurch to the Left, New Labour would be buried, the Blairites would be excluded.
What has happened since Gordon Brown has taken over has been a great tribute to New Labour and to him."
VOICING SUPPORT FOR BROWN, OCTOBER 2008
"I do not think that changing the face at the top is the panacea some imagine.
But the whole of the leadership must remain true to the values and principles that have delivered us success in the past ten years.
It would be odd if we didn't discuss domestic issues... We have a shared interest in Labour's fortunes. [But] the last thing Gordon needs is another full-time adviser.
We have had our ups and downs... But remember, we have known each other for over 20 years.
I don't accept that judgement of him [that Brown's leadership is a disaster] and I really don't think this is simply a matter of personalities.
The reason why Gordon's speech at conference  was a success was that it opened more of a window on to Gordon Brown... The public want to feel a connection, a personal one, with their prime ministers. They know he has a full head of policy ideas and experience. But they also want to know more about him. These are serious times. But that doesn't mean he has to be only about policy, and he showed another side of him."