The sex secrets of the young Barack Obama have been revealed in an authoritative new biography of the ex-president.

Obama slept with his girlfriend Genevieve Cook on their first date, before she wrote him a poem about their 'f***ing' and called their sex 'passionate', the book about the former president reveals.

They also did cocaine together — and after they split she slept with his best friend.

Obama also considered a gay relationship while at college, twice proposed to another white girlfriend, and cheated on Michelle with his ex during the first year of their relationship.

His past is revealed in the 1,078-page biography Rising Star: The Making of Barack Obama, to be published on May 9.

Obama, a new Columbia graduate who was working for a firm that  prepared financial reports at the time, made dinner for Cook at his apartment in Manhattan two weeks after meeting her at a New Year's Eve party and handing her his phone number.

It was the start of a relationship which is one of a series revealed in Rising Star.

The 1,078-page biography is the most comprehensive work ever on Obama and the first to be published since he left office.

It was written after exhaustive research by Pulitzer-prize winning biographer David Garrow, and also reveals how he asked another woman to marry him – and continued a relationship with her while dating Michelle, before she became his wife.

Cook was 25 when she met 22-year-old Obama on New Year's Eve in 1983.

Australian-born Cook was living in her mother and stepfather's Park Avenue apartment at the time, but had been brought up around the world, including — like Obama, Indonesia — as her father was an Australian spy and diplomat.

She wrote about it in a private memoir and said that at the party 'I remember being very engaged and just talking nonstop' with Obama.

'The thing that connected us is that we both came from nowhere – we really didn't belong.'

Their first date involved more than talk however, with Obama cooking at the West 114th Street apartment he shared with two other roommates..

'Then we went and talked in his bedroom. And then I spent the night. It all felt very inevitable,' she wrote in a private memoir, revealed by Garrow.

She spent the night again with him a few days later and rated him highly in bed – even writing a poem to him saying: 'B. That's for you. F's for all the f***ing that we do.'

Garrow reveals that she said: 'Sexually he really wasn't very imaginative but he was comfortable. He was no kind of shrinking "can't handle it. This is invasive" or "I'm timid" in any way; he was quite earthy.'

Their relationship appears to have been deeply sexual, with her writing  that 'all this f***ing' was 'so much more than lust' and also saying in her diary: 'Making love with Barack, so warm and flowing and soft but deep — relaxed and loving — opening up more.'

She also wrote in her diary about 'passionate sex', the book says.

But the couple also used drugs and Cook reveals that Obama was still a cocaine user when they were together.

He would spend time with other friends — Hasan Chandoo, Imad Hussain and Sohale Siddiqi, who he had been friends with at Occidental College, in Los Angeles — and Cook said the trio was taking 'lots of cocaine'.

They were far more prolific users than Obama, who she said probably preferred staying home to read than taking the drug. Chandoo — who was later to become a fundraiser for Obama — was the leader, the book claims.

'For every five lines that somebody did, he would have done half,' Cook said.

The book also notes that Cook and Obama would smoke pot but only at parties and records one time when during tension in their relationship she wrote in her diary that they went to a party and got 'high' on cocaine.

That Obama was still using cocaine in his early 20s is a significant revelation.

He had previously only disclosed that he used it as a teenage student.

The couple split in June 1985, after a year and a half together, the book says.

But she was hardly out of his life — because she became involved with his friend Sohale in September of that year.

She and Sohale did ecstasy together, and then had sex. When she wrote to Obama and told him he replied: 'The news of Sohale and you did hurt.'

He also used - possibly inadvertently - a racial slur to refer to Sohale and the other two Pakistani-born friends, calling them 'the Pakis' in the same letter.

His first name girlfriend in the book was Alex McNear, who is described as a 'beautiful blond' who was the focus of a crushes for many students at Occidental College.

One male student even fantasized that she was 'the most beautiful lesbian'.

Later, writes Garrow, Obama boasted to fellow Illinois state lawmakers at their regular poker games in the early 2000s about a sexual conquest who appears to align with her.

One close acquaintance told Garrow: 'The only woman he ever talked about screwing was some really hot blond chick that he was still proud of.

'He was really proud that he'd banged some super-hot blonde from a super-rich family.'

McNear was not super-rich and Garrow suggests this was an 'exaggerated' version of her upbringing being used by Obama.

However the book is far sketchier on their time together, noting that she knew him in Manhattan as both moved there when he transferred from Occidental to Columbia.

When Obama came to write Dreams From My Father, he created a composite girlfriend from the early 1980s, representing all his white ex-girlfriends.

The book discloses that Jager felt particularity upset by his treatment of his white girlfriends in Dreams From My Father.

Not only did she become part of 'a woman in New York who I loved', their time living together in Chicago for two years was dropped, and — she said — love letters he sent her were the basis for much of the narrative.

'I never understood why he wrote it this way,' she said.

'I wonder if the unedited Dreams is as inaccurate as the published version.'

THE GAY PROFESSOR AND HOW OBAMA CONSIDERED A SAME-SEX COLLEGE AFFAIR

President Obama considered pursuing a gay relationship while he was a college student.

Writing about the former president's two years at Occidental College in Los Angeles, Garrow discloses in Rising Star: The Making of Barack Obama the close relationship Obama had with assistant professor Lawrence Goldyn.

'Goldyn made a huge impact on Barry Obama,' Garrow writes. 'Almost a quarter century later, asked about his understanding of gay issues, Obama enthusiastically said, "my favorite professor my first year in college was one of the first openly gay people that I knew…He was a terrific guy." with whom Obama developed a 'friendship beyond the classroom.'

It was the winter of 1980 when Obama took a political science course at Occidental taught by the openly gay professor, a 1973 graduate of Reed College in Oregon with a PhD from Stanford.

To say that Goldyn was out 'would be an understatement,' a fellow student at the college told Garrow. Goldyn was 'funny, engaging' and 'wore these really right bright yellow pants and open-toed sandals.'

Goldyn was one of the first gay people that Obama knew and Obama said the 'strong friendship that developed helped to educate me.'

Goldyn would remember that Obama was not fearful of being associated with him.

Three years later, writes the author, 'Obama wrote somewhat elusively to his first intimate girlfriend that he had thought about and considered gayness but ultimately decided that a same-sex relationship would be less challenging and demanding than developing one with the opposite sex.'

To say that Goldyn was out 'would be an understatement,' a fellow student at the college tells Garrow. Goldyn was 'funny, engaging' and 'wore these really right bright yellow pants and open-toed sandals.'

The Advocate, a leading gay and lesbian magazine asked President Obama 2009 who had most profoundly influenced his ideas about gays and lesbians, the second person he named — after his mother — was Lawrence Goldyn.

'He was a wonderful guy,' Obama said. 'He was the first openly gay professor that I had ever come in contact with, or openly gay person of authority that I had come in contact with.

President Obama and His Chief of Staff Rahm Emanuel: Members of Same Chicago Gay Bath House

'And he was just a terrific guy. He wasn't proselytizing all the time, but just his comfort in his own skin and the friendship we developed helped to educate me on a number of these issues.'

Goldyn retrained as a doctor and is now an HIV specialist in Mendocino, California.

David Garrow, author of the wrote a Pulitzer Prize-winning biography of Martin Luther King Jr., and is a regular contributor to The New York Times and The Washington Post.

The book, "Rising Star: The Making of Barack Obama" is available on Amazon.com

By Dailymail.com Reporter