Prominent Tory peer Robert Boothby and East End gangster Ronnie Kray went to "homosexual parties" together and were "hunters" of young men, MI5 papers have revealed.

In 1964 it was suggested that Lord Boothby, a popular TV presenter and former MP for East Aberdeenshire, was having an affair with Kray, one of London's most notorious criminals.

The story was broken that July by the Sunday Mirror, which did not name the pair but claimed to have a photo of them together, and they were later identified in a German magazine.

The allegations caused a furore in Westminster and documents show the home secretary, Henry Brooke, was so concerned he summoned the head of MI5 amid fears it might erupt into a scandal to rival the Profumo affair.

Lord Boothby publicly denied having a homosexual or any other close relationship with Kray and allowed the photo of the pair on a sofa at his flat discussing "business matters" to be published, dismissing rumours about his personal life as a "tissue of atrocious lies".

But declassified files released by the National Archives at Kew, west London, show he was much closer to Ronnie Kray and his brother Reggie than he admitted.

According to an MI5 inside "source", who was described as a "self-confessed homosexual", Lord Boothby was in a relationship with his chauffeur, a young "Shoreditch-born former boxer" named Leslie Holt, alias Johnny Kidd, giving him expensive cars and taking him to the opera.

Despite homosexuality being illegal then, the source suggested the relationship was serious, saying: "They are genuinely attached; this is no fly-by-night-affair."

The MI5 report revealed Holt told the source he had introduced Lord Boothby to Ronnie Kray - both widely known to be gay or bisexual - and "they'd been to a couple of (homosexual) parties together".