His claim came after The Mirror published the text of a memo, which he sent to Mr Brown four days after John Smith died from a heart attack in May of that year. In the letter Mr Mandelson, whoresigned over a pounds 373,000 loan from the former paymaster-general, Geoffrey Robinson, warned Mr Brown that he had "a problem in not appearing to be the front runner" against his rival to succeed Mr Smith as party leader, Tony Blair.
Some Brown supporters have argued that the letter showed Mr Mandelson was stealthily betraying his friend and switching allegiance to Mr Blair. But the letter was written at a time when opinion polls and growing opinion in the Parliamentary Labour Party, if not in the unions, was already moving towards Mr Blair.
The letter makes clear that Mr Blair was pulling ahead in the leadership stakes because of his "southern appeal" and suggests Mr Brown would have to choose between going on the attack or withdrawing "with enhanced position, strength and respect". Mr Mandelson said last night: "Apparently desperate for self-publicity The Mirror is doing its best to foment bad relations between Gordon and myself. But we are relaxed about it. We will not be played off against each other." But Paul Routledge, the journalist whose biography of the Chancellor is being serialised by The Mirror, said the memo's emphasis on the potential damage to the party clearly played on Mr Brown's loyalty to Labour.
As presented in the newspaper, Peter Mandelson's intervention was a key factor in persuading Gordon Brown to withdraw from the leadership race. When written, the newspaper observes, there was a moratorium on campaigning until after John Smith's funeral. Yet, Mr Routledge claims, Mr Mandelson was briefing journalists within hours of the death: "It has got to be Blair."
Although not fully quoted before, the letter has been referred to in at least two books on the recent history of the Labour Party and was summarised in Philip Gould's recent book, Unfinished Revolution.
The Latest Labour
Leak In Full
THE LETTER, sent on the Monday after John Smith's death, states: "I thought I should give you my best view of the situation from the media standpoint.
"You are attracting sympathy from the lobby [Westminster journalists] for your position. You are seen as the biggest intellectual force and strategic thinker the party has.
"Most people say there is no one to rival your political `capacity'. I have thought a lot about your fear that you are being written down (out) by the press and I have read everything very carefully. I don't believe your fears are justified. Nobody is saying you are not capable/ appropriate as leader, merely that the timing is bad for you or you have vocal enemies or that you have presentational difficulties.
"You have a problem in not appearing to be the front runner. It's not that people question whether you could catch up - people accept that your support is currently being understated - but that it would be very difficult for Tony to withdraw in your favour (how would it be explained in view of the polls etc?) and that by standing you would trigger Cook and possibly others and this would surely not be in the interests of the party.
"If Tony felt he had to stand and you did too, what would be the consequences? I think you both, and our cause and the party, would be hugely damaged. It would be a gift to our enemies. Because you would be appearing to come in as the second runner, you would be blamed for creating the split. I think the media would attack you and that your standing in the party would suffer.
"The only way to overcome this media resistance to you is to mount a massive and sustained briefing which concentrated on your political skills, ability to unite and manage all sides of the party, dominance in the House, blend of party transition and modernising agenda. I have not encountered much difficulty selling this so far but to be effective it would have to be greatly escalated, begun immediately, and I am afraid, only done by explicitly weakening Tony's position.
"Even then, I could not guarantee success. Ultimately the card the media are playing for Tony is his "southern appeal". He doesn't need to point it out or build it up: it is there firmly in their minds and it is linked to their (and our) overriding question, is Labour serious about conquering the south?
"My fear is that drift is harming you (cf BBC lunchtime news). You have either to escalate rapidly (and to be effective I think I would need to become clearly partisan with the press in your favour) or you need to implement a strategy to exit with enhanced position, strength and respect.
"Will you let me know your wishes? Peter."