Barack Obama considered a same-sex romance and regularly snorted cocaine, an explosive new biography has claimed.

The unauthorised biography by Pulitzer Prize-winning biographer David Garrow, entitled Rising Star: The Making of Barack Obama, details a life of debauchery with drugs and sex long before the politician set his sights on office.

Former girlfriend Genevieve Cook fell for a then 22-year-old Obama after the pair met at a party in 1983. Recalling her passionate romance with the Columbia graduate three years younger than her, Cook told Garrow that they slept together within days.

Australian-born Cook was so impressed with his bedroom skills that she felt compelled to write her lover a poem which included the line: "B. That's for you. F's for all the f***ing that we do."

She told Garrow: "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."

According to the tome, Obama allegedly enjoyed many more flings with white women before meeting his wife Michelle. It also claims that even after he found love with Michelle, he cheated on her several times with former love Sheila Miyoshi Jager, who is now a college professor. She told Garrow she "always felt bad" about their liaisons.

The book also lays bare details his close relationship with openly gay assistant professor Lawrence Goldyn and suggests it may have influenced him when he allegedly started exploring his own sexuality. He allegedly considered having a gay relationship because he thought it would be "less challenging" than being heterosexual.

"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."

In 2009, Obama spoke very highly of Goldyn, crediting him for influencing his stance on the LGBT community. He said at the time: "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."

Cook also delves into Obama's history with drugs alleging that he would take "lots of cocaine" with friends Hasan Chandoo, Imad Hussain and Sohale Siddiqi. "For every five lines that somebody did, he would have done half," Cook writes.

Although Obama has not responded to the book's claims, he previously admitted to dabbling in marijuana and cocaine as a teenager, but never his 20s. "It was reflective of the struggles and confusion of a teenage boy," he said at a meeting of the American Society of Magazine Editors in 1996. "Teenage boys are frequently confused."

Rising Star: The Making of Barack Obama is scheduled for release on 9 May.