The file detailed alleged attempts by the Paedophile Information Exchange (PIE) to infiltrate government while seeking funding and trying to persuade MPs to legalise sex with children.
Put together in the early 1980s by the late Baroness Castle of Blackburn, it named about 16 high-profile politicians who “enhanced PIE’s ambitions”.
As well as key members of both the Commons and Lords, she found that senior police officers, headteachers and clergy had links to PIE.
Baroness Castle, who at the time was Euro MP Barbara Castle, took the claims to Don Hale, a campaigning newspaper editor in Bury, Lancs.
But Mr Hale says an astonishing operation kicked in to silence the claims.
He says he received a visit from Rochdale’s Liberal MP Cyril Smith, now widely believed to have been a prolific paedophile.
Mr Hale, 61, said: “Cyril tried to persuade me that it was ‘all poppycock’.
“He said Barbara had her ‘knickers in a twist’ since leaving the House and had become bored with wine lakes and sugar mountains in Europe. He played down the whole episode and wanted an assurance that I wouldn’t run anything.
“Barbara had many original notes and I copied quite a few and retained others.
“I agreed to run something the following week based on her views and concerns but obviously had to contact certain members named and the Home Office for their responses.”
He went on: “Each call was met with shock horror as to why I should be wasting my time asking these ‘daft’ questions as nothing was happening within Parliament.
“Most asked where I had got the information from, how long I had had it and what I intended to do with it?
“When I explained the detailed nature of the information available and that I couldn’t reveal my source, you could almost hear a pin drop as officials were unsure as to what to say or do.”
Mr Hale added: “I was sworn to secrecy by Special Branch at the risk of jail if I repeated any of the allegations.
“When I met Barbara again, she apologised for the ‘hassle’ caused and reluctantly admitted she was fighting a formidable foe.”
The revelations follow claims of a cover-up of a dossier detailing a Westminster paedophile ring by the late MP Geoffrey Dickens.