Socialite divorcee Mary Pinchot Meyer, who was close friends with the Kennedys is known for her lengthy affair with the president.

But a new book, by author Peter Janney, suggests she was shot in a CIA cover up, after she became preoccupied with Kennedy’s assassination.

Agents staged a shooting to make it look like she died in a would-be sexual assault that turned violent, on October 12 1964, 11 months after Kennedy’s death, says the theory.

Pinchot Meyer’s ex-husband, Cord Meyer, was a CIA agent, and the pair were part of Georgetown’s starry social set, along with Kennedy and his wife Jacqueline Kennedy.

Police charged day labourer Ray Crump Jr. with Pinchot Meyer’s murder, but detectives never found a gun, and was acquitted after an eyewitness described the killer as much bigger than the defendant.

The case became one of Washington’s most infamous unresolved murders.

The book is called Mary’s Mosaic: The CIA Conspiracy to Murder John F. Kennedy, Mary Pinchot Meyer, and their Vision of World Peace.

The author claims that the socialite and painter would often bring LSD and marijuana to her meetings with the president, and urged him to find peaceful solutions to the Cold War and the Cuban missile crisis.