A powerful paedophile network may have operated in Britain protected by its connections to Parliament and Downing Street, a senior Labour politician suggested yesterday.

Speaking from the back benches of the House of Commons, Tom Watson, the deputy chairman of the Labour Party, called on the Metropolitan Police to reopen a closed criminal inquiry into paedophilia.

Indicating his anxiety that there had been an establishment cover-up, Mr Watson referred to the case of Peter Righton, who was convicted in 1992 of importing and possessing illegal homosexual pornographic material.

Righton, a former consultant to the National Children’s Bureau and lecturer at the National Institute for Social Work in London, admitted two illegal importation charges and one charge of possessing obscene material. He was fined £900.

At Prime Minister’s Questions, Mr Watson said the evidence file used to convict Righton “if it still exists, contains clear intelligence of a widespread paedophile ring”.

He told a hushed Commons: “One of its members boasts of a link to a senior aide of a former Prime Minister, who says he could smuggle indecent images of children from abroad.

“The leads were not followed up, but if the files still exist, I want to ensure that the Metropolitan Police secure the evidence, re-examine it, and investigate clear intelligence suggesting a powerful paedophile network linked to Parliament and No 10.”

In the aftermath of Mr Watson’s remarks, media outlets speculated that he was referring to the late former Prime Minister Sir Edward Heath – who was the subject of unsubstantiated rumours about sex with under-age boys – or to Sir Peter Morrison, a former Downing Street aide who died in 1995.

However, The Independent understands that Mr Watson’s comments were not aimed at either Sir Edward or Sir Peter, but at a living person associated with Margaret Thatcher’s administration.

They are thought to involve the activities of the Paedophile Information Exchange, a pro-paedophile group in existence between 1974 and 1984, which believed there should be no age of consent.

Responding to the remarks, David Cameron said the MP had raised “a very difficult and complex case”, adding he was unclear which former Prime Minister Mr Watson was referring to.

Criticising the BBC’s record on Savile – who was never caught and died last year aged 84, the Prime Minister said: "These allegations do leave many institutions - perhaps particularly the BBC - with serious questions to answer - I think above all the question, 'How did he get away with this for so long?'.”