Former American President John F Kennedy snorted cocaine with actor Peter Lawford while the two stayed at Frank Sinatra's Palm Springs house in the late 1950s, according to an excerpt from a tell-all book written by Sinatra's former valet.

Writing about the close friendship between Sinatra and the future US president, George Jacobs said that although the Rat Pack singer knew of Kennedy's weakness for women - he arranged liaisons for him - he would not have approved of his drug use.

In an excerpt from his forthcoming book Mr S, released in the June edition of Playboy Magazine, Jacobs said he was present on several occasions "when Peter Lawford and the future president did lines of cocaine together in Lawford's guest rooms".

"The first time it happened Jack must have seen the shocked look on my face. 'For my back, George' Kennedy said to me with his bad-boy wink," Jacobs wrote, adding that Lawford pleaded with him not to tell Sinatra.

Lawford was married at the time to Kennedy's sister Pat and both men were frequent guests at Sinatra's Palm Springs compound.

Jacobs, who was Sinatra's valet from 1953 to 1968, said Kennedy had an "endless obsession with sex and gossip. He wanted to know all the Hollywood dirt". But Jacobs said he never told Sinatra about Kennedy's cocaine habit.

"I wasn't about to break the bad news about Jack, who Mr S had put on a pedestal. Sex and alcohol may have made Jack a better man in Sinatra's sight. Cocaine was a different story," he wrote. Jacobs's book about his life as Sinatra's right-hand man is to be published in June by HarperCollins.

A new biography of Kennedy by historian Robert Dallek published this month disclosed that in the last eight years of his life Kennedy was taking as many as eight medications a day for a variety of medical problems including back pain and Addison's disease, a life-threatening lack of adrenal function.

Presidential historian Dallek concluded from newly released documents from the John F Kennedy Library in Boston that Kennedy, like Bill Clinton decades later, may have had an affair with a young White House intern, an attractive 19-year-old woman with limited office skills.

Dallek's biography of the 35th president, An Unfinished Life: John F. Kennedy, 1917-1963, containins details of the supposed affair.

The author's conclusions stem from a 1964 interview with Barbara Gamarekian, a press aide in the Kennedy White House, who recalled her experiences for an oral history project for the Kennedy Library.

"Obviously, she did have sort of a special relationship with the president," Gamarekian said of the woman.

"She couldn't type... She could answer the phone and she could handle messages and things, but she was not really a great asset to us," Gamerekian said in the interview.

But Kennedy brought the intern along on presidential trips, according to Gamarekian.

In a Dateline NBC programme, Dallek said, "Apparently her only real skill was to provide sexual release for JFK on these trips, and maybe at the White House."

The transcript of Gamarekian's recollections includes 17 pages touching on the alleged affair, which Gamarekian had originally asked the Kennedy Library to keep sealed. Gamarekian allowed Dallek to read the pages for his research, and the library has now made public the entire transcript.

New York's Daily News splashed the story on its front page under the headline: "JFK had a Monica."

Kennedy's legendary sexual exploits, reportedly involving numerous women including in some accounts Marilyn Monroe, came to public notice only after his assassination in 1963. - Reuters