The prime minister is to take over a key session of the World Economic Forum in Davos which had been promised to the chancellor. Blair will now replace Brown on the platform alongside Bill Gates, head of Microsoft, and Thabo Mbeki, the South African president.

The move comes after last week’s last-minute decision by Blair to hold his monthly press conference at the same time as a long-trailed speech by Brown on Africa and reducing world poverty.

The chancellor, who is now unlikely to attend the conference in the Swiss resort, was to have taken his flagship poverty message to Davos. It will be seen as another snub by Blair to the man who wants to succeed him as prime minister. Blair will have known that he would get star billing at the event even if his chancellor was attending.

However, insiders have revealed that No 10 rang the organisers to request the meeting with Gates and Mbeki be brought forward a day to January 27.

Blair has commitments in London that day. A senior Blairite said of the current tension: “Tony rightly takes the view that he is the boss and when — and if — Gordon becomes prime minister, then he can make the decisions and take the lead.”

The disclosure will fuel the men’s rivalry, which has already left their relations at an all-time low. Labour MPs warned last night that Blair’s renewed assertion of authority was threatening to derail Labour’s general election campaign.

One described it as “the leadership at war”. Tension increased this weekend with the impending publication of two books on their relationship, exposing a series of bitter disagreements.

One, a semi-authorised biography of the chancellor called Brown’s Britain, reports that Blair promised Brown repeatedly over a period from late 2003 to July last year that he intended to stand down and only wanted Brown’s support in the meantime before an orderly handover could be arranged.

But it alleges that Blair changed his mind and that has led to the relationship degenerating into “mutual animosity and and contempt.”

Another book, with which Blair is co-operating, is expected to criticise Brown heavily. Blair is co-operating with a study of the rivalry by the commentator Andrew Rawnsley, whose 2000 book Servants of the People: the Inside Story of New Labour, savaged Brown.

The prime minister is understood to have met the author, who previously quoted Blairite sources accusing the chancellor of being “psychologically flawed”.

Brown has yet to be invited to be interviewed. At his press conference last week, Blair failed to reassure the chancellor and his supporters that he would retain him in the post after the election.

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