King, pictured with his wife Coretta, is believed to have had sexual affairs with up to 45 women according to FBI files

Martin Luther King Jr had extramarital affairs with nearly four dozen women, fathered an illegitimate child and allegedly encouraged the rape of a parishioner by a fellow Baptist minister, according to FBI files.

Details of the civil rights campaigner’s private life have been unearthed by a renowned biographer who discovered them in tranches of declassified records compiled and held by the FBI.

David Garrow, the historian, predicted that the revelations would force future generations to reassess the legacy of King, who was shot dead in Memphis in 1968, aged 39. Garrow’s 1987 biography of the revered Baptist minister, entitled Bearing the Cross, won that year’s Pulitzer prize.

In an article to be published in Standpoint magazine next month, Garrow describes notes on King that were