The "diary wars" between New Labour's founding fathers intensified yesterday when friends of Tony Blair flatly denied that he had tried to postpone publication of Peter Mandelson's memoirs.

Allies of the former prime minister suspect that a series of stories claiming he is miffed that Mandelson has beaten him into print have been fed to the press to publicise the peer's "gossipy" book, The Third Man, out this week.

One source close to Blair – whose own book is not out for another six weeks – said he was mystified by the claims of manoeuvring, which were "simply untrue". The strong denial by the Blair camp will feed suspicions that the story is an elaborate spin exercise with all the hallmarks of New Labour in its prime. The former business secretary said he had decided to publish now to be helpful to candidates for the Labour leadership. They could "draw lessons from my book" rather than "face having my book published after he's become leader and being dragged back into the past," he said.

But a former senior aide to Gordon Brown accused Mandelson of putting his literary ambitions before even his role running Labour's ill-fated election campaign earlier this year. "Peter wasn't focused on the campaign at all. Clearly his only thoughts were for his book," said Charlie Whelan, political director of the Unite union.

The row began when the Observer's Vanessa Thorpe wrote that Mandelson's camp, including his publishers HarperPress, were saying that Blair had called Rupert Murdoch, who owns the publishing house, to ask for a delay so that his own book was not beaten to the shelves.

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