Prince Philip has been named in a batch of FBI files detailing his role in an infamous sex and espionage scandal in the 1960s.

The Profumo affair rocked the British establishment in the early years of the decade when married Secretary of State for War John Profumo denied he had a sexual affair with a teenage showgirl, Christine Keeler in the House of Commons. He was forced to resign after proof of the affair emerged and he was found to have lied to the house.

The scandal became a matter of national security because Christine had also been sleeping with a Russian spy at the height of the Cold War.

There had long been speculation about the Duke’s relationship to the affair, with the newly released US Department of Justice files showing that the FBI was alerted to Prince Philip being personally “involved” with Christine Keeler and her friend Mandy Rice-Davies.

The files in question are a crucial memo written by then-director of the FBI J Edgar Hoover, the Mail on Sunday has reported. The claim against the Duke of Edinburgh comes from a US businessman involved in industrial espionage called Thomas Corbally. He agreed to be interviewed by the FBI about his friendship with well-connected osteopath Stephen Ward, who took his own life after being prosecuted for living off the immoral earnings of the two women.

The memo, sent to the US embassy in London on June 20, 1963, reads: “Corbally also stated there was a rumour Prince Philip may have been involved with these two girls.”

The Profumo affair is one of the most high-profile scandals to have swept through British society in the 20th Century. Keeler, who was born in Middlesex, was just 19 years old at the time of the affair. She had moved to London when she was a teen started working at Murray’s Cabaret Club in Soho.

There she met Dr Ward, a “fixer” known to procure beautiful young women for members of the British establishment. Dr Ward introduced her to Tory minister John Profumo in 1961 at a glitzy party held by Lord Astor.

When she was 19, she had been sleeping with both Profumo, then 48, and a Russian spy named Evgeny Ivanov. Profumo told the Commons that he had not been involved in a relationship with the young woman. But it wasn’t long before the press revealed his lies and he was forced to resign in June 1963. Due to the increased press attention, Keeler sold her story to the News of the World for £23,000.

There were allegations that Ivanov had asked Keeler to ask the minister the date when the government of West Germany might receive US nuclear missiles.