A new biography of Barack Obama has revealed the US president's fondness for marijuana as a high school and college student, detailing his membership in an informal pot-smoking group in Hawaii called the Choom Gang.

Mr Obama has readily conceded that he smoked marijuana in his younger days, but the forthcoming book Barack Obama: The Story by Pulitzer-prize-winning historian David Maraniss provides much greater detail into his activities.

Barack Obama ... a new book details his alleged use of drugs. Credit:AFP

The book does not officially go on sale until June 19, but excerpts from it have already revealed details of his past romantic liaisons.

The new excerpts, which were widely distributed over the internet following their publication on Friday on the website buzzfeed.com, say that when Mr Obama attended the elite Punahou School in Hawaii, he went by the name Barry and was a member of a group of boys called the Choom Gang who loved to play basketball and smoke marijuana.