Excusing himself, he left the table. But, unknown to his guests, he walked in humiliated fury not to the bathroom, but to the White House Map Room. Waiting for him were FBI doctors and a federal prosecutor, there to take his blood sample to see of it matched the DNA on Ms Lewinsky’s now infamous semen-stained dress.

This extraordinary episode, which remained secret until yesterday, is recounted in an explosive new book by Louis Freeh, the FBI Director during the 1990s.

Mr Freeh writes for the first time about his appalling relationship with the President who appointed him, and the endless stream of scandals that made Mr Clinton the constant target of FBI investigations.

“The problem was with Bill Clinton — the scandals and the rumoured scandals, the incubating ones and the dying ones never ended,” Mr Freeh writes in My FBI: Bringing Down the Mafia, Investigating Bill Clinton, and Fighting the War on Terror.

“Whatever moral compass the President was consulting was leading him in the wrong direction. His closets were full of skeletons just waiting to burst out. We were preoccupied in eight years with multiple investigations.” The scandals included the Whitewater inquiry and Mr Clinton’s affairs with Ms Lewinsky, Paula Jones and Gennifer Flowers.

The need to obtain Mr Clinton’s blood sample was the most unsavoury element of the FBI’s investigation of the Lewinsky saga, Mr Freeh says.

The White House intern, whose affair with Mr Clinton led to impeachment proceedings, had kept a Gap dress stained with his “genetic material” as proof of their relationship. She later revealed its existence to Kenneth Starr, the independent counsel investigating the former President. The dinner party subterfuge was “like a bad movie”, Mr Freeh writes. “But we did it, very carefully, very confidentially.”

John Harris, a Washington Post reporter, provides more detail about the Map Room encounter in his biography of Mr Clinton, The Survivor.

“Clinton’s face was flushed with anger as he rolled up his sleeve while one of his Navy physicians drew the sample. A prosecutor and federal agent fixed their gaze on the vial the entire time, fearful that Clinton’s team might try a surreptitious switch.” Such was the mutual distrust between Mr Starr and Mr Clinton that the former President’s lawyer ordered a second blood sample in case Mr Starr resorted to dirty tricks, according to Mr Harris.

Mr Freeh also writes of a conversation between Mr Clinton and Crown Prince Abdullah of Saudi Arabia in the aftermath of the Khobar Towers bombing that killed 19 US servicemen in Dhahran in 1996. He claims that Mr Clinton used the occasion to solicit a donation for his presidential library.

Mr Freeh says that Mr Clinton refused to insist that the Crown Prince allow the FBI to question suspects held in custody in Saudi Arabia. “Bill Clinton raised the subject only to tell the Crown Prince he understood the Saudis’ reluctance to co-operate and then he hit Abdullah up for a contribution to the Clinton Presidential Library.”

Newt Gingrich, the former Republican House Speaker and erstwhile Clinton nemesis, said on the Fox television network: “If Louis Freeh is prepared to swear on oath that he knows that President Clinton was asking foreign leaders for money . . . this has to be a criminal offence of the first order.”

Mr Freeh was appointed by Mr Clinton in 1993, but relations between the two became poisoned. Mr Freeh writes that to distance himself from the scandals, he refused a White House pass that would have allowed him access without signing in. “I wanted all my visits to be official,” he said.

They clashed repeatedly, including over an FBI inquiry into alleged Chinese efforts to funnel campaign donations to Democrats, an inquiry that Mr Freeh never told Mr Clinton about. Mr Clinton soon referred to the FBI chief as “F****** Freeh”, seeing him as an agent for the Republicans.

Mr Freeh resigned from the FBI in 2001, three months before the September 11 terrorist attacks. He was harshly criticised by the commission that investigated the atrocity.

Jay Carson, Mr Clinton’s spokesman, said: “This is clearly a total work of fiction, written by a man who’s desperate to clear his name. It’s unfortunate that he’d stoop to this level in his desperate attempt to rewrite history. Freeh’s claims about library fundraising are more untruths from a book that’s chock-full of them.”

Daniel Benjamin, a former Clinton aide, said that the former President “pushed the Crown Prince quite hard” over the Khobar Towers investigation, and won Saudi co-operation that led to indictments.

TENSIONS BETWEEN THE WHITE HOUSE AND THE FBI

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