In The Quest for Graham Greene, author WJ West contrasts the writer's anti-Americanism with his unwitting involvement - and that of others such as Charlie Chaplin - in the illegal scams.
"It must have been acutely embarrassing for Chaplin and Greene, with their political sympathies, to have been caught up in the seediest backwaters of international capitalism," writes Mr West, who says the author thought he was merely using tax avoidance schemes.
The book also reveals that Greene had been a member of a communist cell at Oxford, the first student group of its kind, and that the security services were unaware of this when he later joined MI6. This may have been because his uncle, Sir Graham Greene, who was close to both Naval Intelligence and MI6, had "wiped the slate clean".
Greene's near-obsession with Catholicism, the book says stemmed not from his desire to marry his Catholic wife, Vivien, but from youthful hero worship of figures such as the Irish nationalist Michael Collins and his support for the Catholic community in the Palatinate as a young man.
Novelist and author Mr West, who has also written about George Orwell and his work at the BBC, said yesterday he regarded Greene as one of the most important figures in British literature this century, and possibly ever.
"You have to go back a long way to find a writer who was so closely involved in the politics and life of this country.
"He is a far more serious figure in the political history of the 20th century than has been realised," said Mr West, whose book is published by Weidenfeld & Nicolson on 23 June.
The book explores Greene's lasting relationship with the spy Kim Philby, and reveals that they had a common bond; each had a relative who was locked up on suspicion of having fascist tendencies in the Second World War.