A former Tory cabinet minister is to be questioned by detectives after a video filmed at an underage sex party was seized by police.

The video, along with a number of photographs, allegedly places the ex-MP, a household name, at a depraved orgy organised by a paedophile.

The photographs were seized from a known child sex offender earlier this year and the video is believed to have come from another source.

The veteran Tory, who we cannot name for legal reasons, is understood to deny any wrongdoing. But an alleged victim, who claims to have been at the event three decades ago, has come forward.

Detectives used pictures of the alleged victim when he was a boy to cross reference with those of him at the party.

Sources close to the investigation have made known the shocking new revelations to the Sunday Mirror and investigative news website Exaro.

We previously revealed that the former minister was being investigated by detectives over allegations of child abuse.

The key witness said: “The police tell me that they have photographic evidence that I went to these parties. They have a photograph of me as a child, and it matched some other photographs that they have of me. They have a bit of film as well.”

Officers are due to begin a separate operation in the New Year into the sex party allegations as a spin-off from Operation Fairbank, which last year looked into allegations of abuse by politicians at the Elm Guest House in south west London.

While the video and photographs allegedly place the ex-minister and the victim at a party where boys were supplied to men, they do not prove that the former politician carried out any abuse.

But one source, a specialist in child protection, said: “This is potentially bombshell stuff. I have long been aware of the fact that these parties took place in London. This could be very significant.”

Detectives believe that some of the sex parties – some of which are believed to have been attended by paedophiles Jimmy Savile and MP Cyril Smith – were organised by Britain’s most notorious child abuser, Sidney Cooke, as we revealed in February.

Cooke led the ring of four jailed for killing Jason Swift in Hackney, East London, after gang-raping him in 1984.

The alleged victim claims he was ­trafficked, along with other children, to Holland by Cooke’s gang.

Scotland Yard’s paedophile unit has been working with Dutch police, and an officer from Amsterdam attended an interview by Met detectives with the key witness.

The Sunday Mirror told in February how the minister had been photographed by police in 1986 entering a property where one of the sex parties was being held, but no arrests were made.

Cooke, now 86, would pick up the unsuspecting teenage boys from streets around Kings Cross. He would drive them to places across North London where paedophiles lay in wait to rape them repeatedly.

A former officer, who worked on Operation Orchid which convicted Cooke and his gang, claimed they had taken pictures of the minister and that 16 members of an alleged VIP paedophile ring were due to be arrested.

But the day before the arrests were to be carried out, detectives were told the operation had been disbanded.

Scotland Yard said they would not comment on an on-going investigation.