David Cameron has ordered an inquiry to "find all the answers" into what happened to a dossier on abuse by an alleged paedophile ring within Westminster in the 1980s, as it is alleged sitting parliamentarians are being investigated.
The prime minister has ordered the fresh review by the most senior official at the Home Office into the dossier, which was handed to the then home secretary, Leon (now Lord) Brittan by the Conservative MP Geoffrey Dickens in 1983 but has disappeared.
The Director of Public Prosecutions has been urged to look into this.
Operation Fernbridge, the police investigation into the ring, has more than 10 current and former politicians on its list of alleged child abusers it is investigating, the Daily Telegraph reported.
MPs or peers from the three main political parties are on the list, the paper reported, adding they included "household names".
The list includes the late MPs Cyril Smith and Sir Peter Morrison.
Cameron insisted that he understood the concerns which had been raised about the missing file.
"That's why I've asked the permanent secretary at the Home Office (Mark Sedwill) to do everything he can to find answers to all of these questions and to make sure we can reassure people about these events. So it's right that these investigations are made," he said.
However shadow home secretary Yvette Cooper said the move did not go far enough and called on Cameron to establish a full investigation into all the allegations of historic child abuse.
She said the government should also publish the full findings of a review commissioned last year by Sedwill which found the dossier had not been retained by the department.
"The prime minister is right to intervene to demand a proper investigation into the allegations of child abuse not being acted upon by the Home Office, because we have not had answers from the Home Secretary," she said.
"The prime minister should ensure that the action now taken by the Home office amounts to a proper investigation into what happened and also that Theresa May publish the full review conducted in 2013.
"We also need assurance that the police have been given full information now and are investigating any abuse allegations or crimes that may have been committed.
Labour MP Simon Danczuk, who carried out an investigation into abuse by Cyril Smith and who raised the issue of what happened to the Dickens' file at a hearing of the Commons Home Affairs Committee, said there needed to be a full public inquiry.
He said: "The prime minister knows that there is a growing sense of public anger about allegations of historic abuse involving senior politicians and his statement represents little more than a damage limitation exercise. It doesn't go far enough.
"The public has lost confidence in these kind of official reviews, which usually result in a whitewash. The only way to get to the bottom of this is a thorough public inquiry."