A powerful paedophile ring in Downing Street alleged by Tom Watson MP has revived memories of a sinister child sex network, the Paedophile Information Exchange, that infected areas of public life nearly three decades ago.

It was a network that was believed to include a sex offender and senior aide to prime minister Margaret Thatcher and who was referred to in parliament by Watson. The Paedophile Information Exchange (PIE) campaigned for the abolition of the age of consent.

The West Bromwich East MP named Peter Righton as the link between the child sex ring and the senior Downing Street aide. Righton was also a member of the PIE. He was convicted of importing child pornography from the Netherlands in 1992.

Watson called for a new police investigation into the alleged ring. In parliament, he cited evidence in the trial of Righton and called for the case file to be reopened if possible.

Watson said: "Though Righton was the subject of a 1994 BBC profile, The Secert Life of a Paedophile, little had been done to follow up the leads from the case. A specialist unit in Scotland Yard had the material which supplemented a wider investigation into organised paedophile rings in children's home."

According to The Daily Mirror, it was claimed that material seized at Righton's home contained letters from known and convicted paedophiles.

Watson added: "The contact, who has seen the letters, claimed that one paedophile in particular was of great concern. He said that the paedophile, who worked with children, boasted a key aide to a former PM who could get hold of indecent images of children."

PIE which is now outlawed, also had links with another BBC presenter who was investigated over child sex allegations in the late 1980s, alleged the Daily Mirror.

Like Savile, the unnamed star was accused of using a charity as a cover to abuse vulnerbale children. The charity was set up by a PIE member in the 1980s offering yachting classes to vulnerbale and underprivileged children.

The BBC presenter was investigated after police became aware of allegations he was abusing boys during sailing trips. No charges were ever brought against the star for reasons that remain unclear.

According to the Mirror, a child protection source said: "The presenter was going out in a boat with vulnerable children and a leading former member of PIE. The charity was being used as a way of taking indecent pictures of the boys and there was also physical abuse occurring."

Increasingly, it would appear that PIE was at the centre of a paedophile ring that included top celebrities and poiticians, which the widening revelations about disgraced TV presenter JImmy Savile are set to expose.

How Campaign Group Fought for Respectability for Paedophiles

Founded in 1974, the PIE was a legitimate group with links to established organisations which would no doubt be the cause of a few red faces, today.

Righton, for example, had access to the corridors of power, thanks to his status as a national authority on childcare, and numbered among his contacts Virginia Bottomley, the then health secretary.

In an embarrassing chapter in its history, civil rights lobby group Liberty welcomed PIE into the fold, in 1978. Liberty, then known as the National Council for Civil Liberties and counted a much younger Harriet Harman as its legal officer.

Newspapers were attacked in campaigns against media coverage of paedophile cases by the group. PIE even contributed a submission to a Whitehall committee scrutinising child protection legislation.

As well as fighting its cause, PIE members carried out surveys among themselves. One such poll revealed that most of them were attracted to girls aged between eight and 11.

But in 1984, chairman Steven Adrian Smith fled the country ahead of a trial over adverts in the group's magazine, Magpie, which allegedly promoted sex abuse of children.

His predecessor, Tom O'Carroll, had been convicted in 1981 of distributing child porn. The closing net of law enforcement triggered the group's final collapse. But its toxic legacy could yet rock Britain's political and entertainment establishment.