One of Tony Blair's closest allies has claimed the former prime minister believed Gordon Brown "could never beat" Tory leader David Cameron at the polls.
Mr Blair also described his chancellor and successor in Number 10 as a "liar", Lord Levy said.
His comments - categorically denied by Mr Blair - come in the controversial peer's memoirs, serialised in the Mail on Sunday newspaper.
Mr Blair "told me on a number of occasions he was convinced Gordon 'could never beat Cameron'," Lord Levy wrote. He said the former premier felt he could have won a fourth term had he not stood down last summer.
"But Gordon? 'He can't defeat Cameron,' Tony told me. Blair believed Cameron had major strengths - political timing, a winning personality and a natural ability to communicate to Middle England that Gordon would be unable to match," Lord Levy added.
Mr Blair's spokesman said: "Tony Blair doesn't agree with the views attributed to him by Lord Levy and fully believes Labour with Gordon Brown's leadership can win the next election.
"Tony Blair said when he stood down that he would be 100% loyal to Gordon Brown and that continues to be the case."
Lord Levy's claims heap further pressure on the Prime Minister as he struggles to maintain his authority amid Labour rebellions over taxation and the detention of terrorist suspects.
He said Mr Blair felt Mr Brown was behind an attempt by Labour MPs in 2006 to oust him from Downing Street and Labour Treasurer Jack Dromey's claim that he had been kept in the dark about the secret loans that led to the "cash-for-honours" inquiry.
"He kept saying he had never realised how duplicitous Gordon was - and what a 'liar'," Lord Levy wrote. "I never assumed - Tony certainly never did - that it was about Jack Dromey. It was about Gordon Brown."
