The former paymaster general's book is due to be published in October, at a time when Tony Blair may be considering a cabinet return for his close ally Mr Mandelson. The former secretary of state for trade and industry has been tipped to succeed Mo Mowlam as Northern Ireland Secretary.
The Prime Minister is said to be worried that the book will "reopen old wounds" and has asked Anji Hunter, his special assistant, to hold talks with Mr Robinson in an attempt to limit the extent of his disclosures.
Mr Robinson's book - working title, The Unconventional Minister - is expected to say that Mr Mandelson asked him for the loan. It helped him to buy a pounds 465,000 house in Notting Hill, west London, in 1996. Mr Mandelson has suggested that Mr Robinson, a millionaire, offered him the money and instigated the ill-fated arrangement by urging him to get settled in a new London home before the 1997 general election.
Despite Mr Robinson's generosity, his book is expected to reveal that Mr Mandelson did not even invite him to his housewarming party. He found out about the event only when Sue Nye, political secretary to the Chancellor, Gordon Brown, returned to the Treasury from the Notting Hill house. "I bloody paid for it," Mr Robinson is said to have remarked.
The book may also dent Mr Mandelson's comeback hopes by revealing details about his rift with Mr Brown. Mr Robinson was one of the Chancellor's closest allies and tried to repair relations between the two men, which never recovered from Mr Mandelson's decision to back Mr Blair for the Labour leadership in 1994.
Mr Robinson has told friends he is ready to ignore the rules that restrict disclosures by former ministers about discussions within government. His book may highlight Mr Mandelson's work, first as the minister without portfolio and then as trade secretary, the post from which he resigned last December after the loan was revealed.
Mr Brown is understood to have pleaded with Mr Robinson not to go ahead with his project, but to no avail.
"We don't need any more books," said a source close to the Chancellor - a tacit admission that Mr Brown had been damaged by a biography of him that revealed his continuing disappointment at not becoming Labour leader.
Senior Labour sources have launched a pre-emptive strike against Mr Robinson in an attempt to limit the damage from his book. Yesterday, they claimed he was "a bitter man" at being forced to resign along with Mr Mandelson.
Mr Robinson is understood to believe he was undermined by Downing Street before the disclosure of his loan. He suspected that No 10 could have stemmed the flood of press disclosures about his business affairs before becoming a minister. But a government source said: "There was nothing we could do. It was not in our power to stop it."
Mr Blair's allies hope Mr Robinson's book will delay rather than stop Mr Mandelson's return to ministerial office. The Prime Minister is keen to bring him back, and was tempted to send him to the Northern Ireland Office before Ms Mowlam won her battle to keep her post in the reshuffle.Reuse content