A dossier of evidence of an alleged paedophile ring which was believed to have been lost has been handed to a Labour MP who has been at the forefront of demands for justice for victims.

The dossier is believed to be a copy of the evidence handed to then Home Secretary Leon Brittan by Conservative MP Geoffrey Dickens in 1984.

A review of the Home Office's handling of child abuse allegations dating back to the 1970s failed to locate a copy of the file. The review, by NSPCC chief executive Peter Wanless, reported last year that there was no evidence to support claims of an official cover-up, but warned it was impossible to draw firm conclusions because of shortcomings in the paper records from the time.

John Mann said that the file was handed to him by the same individual who had provided it to Mr Dickens in the 1980s, after it was compiled by former Tory MPs Sir Victor Raikes and Anthony Courtney - both now dead.

The Bassetlaw MP said he would pass it on to the Metropolitan Police to assist them with their investigations into historical sex abuse allegations.

"There were two files that Geoffrey Dickens gave to Leon Brittan in 1984, this is the second file and the person who gave it to Geoffrey Dickens has now given a copy to me," Mr Mann told the Press Association.

"Two questions now arise. Firstly, why were the contents of the file not investigated? Secondly, why was the Prime Minister unable to find this file when he instigated the Wanless Review last year?

Mr Mann said the dossier included a list of alleged paedophiles, including "a small number of names which would be recognised by people who follow politics", but declined to reveal the identities of those named.

"There are also background documents which will be of interest to police now and would have been of interest to police at the time," he said.

Mr Mann said that he was "confident" that the dossier was genuine and that the person who passed it to him was the same individual who provided it to Mr Dickens and would be willing to speak to police now.

"The files that are there, I know are valuable to their ongoing investigation," he said. "It may lead to new investigations as well. I would be surprised if it didn't, but that is a decision for them to make, not me."