The Home Secretary is to address MPs over allegations of organised child sex abuse at Westminster in the 1980s

A Hillsborough-style independent inquiry is to investigate the handling by public bodies of allegations of child sex abuse, Home Secretary Theresa May has announced.

The announcement in the House of Commons came after Prime Minister David Cameron promised to leave "no stone unturned" in seeking the truth about widespread allegations of a paedophile ring with links to the establishment in the 1980s.

The inquiry will be given access to all Government papers it requests, and could be converted into a full public inquiry if its chairman feels it is necessary. It is unlikely to report before next year's general election, but Mrs May promised that an update on its progress will be given to Parliament before May 2015.

Like the probe into the Hillsborough football disaster, which reported in 2012, it will be a non-statutory inquiry initially focusing on documentary evidence, but it will have the power to call witnesses, subject to the need to avoid prejudicing any criminal investigations.

Meanwhile, a separate review, led by NSPCC chief executive Peter Wanless, will look into an investigation conducted last year into the Home Office's handling of child abuse allegations made over a 20-year period, as well as the response of police and prosecutors to information which was passed on to them.

Mrs May said she was confident that the work commissioned last year by Home Office permanent secretary Mark Sedwill was "carried out in good faith", but added: "I know that with allegations as serious as these the public need to have complete confidence in the integrity of the investigation's findings."

Mr Wanless is expected to report within eight to 10 weeks and will look at concerns that the Home Office failed to act on allegations of child sex abuse contained in a dossier handed over in by former Tory MP Geoffrey Dickens to then Home Secretary Leon Brittan in 1983.

Last year's investigation found 13 items of information in Home Office files about alleged child abuse dating back to the period 1979-99, and passed police details of four of the items about which they were not already aware. But Mrs May told MPs that, while records of a number of letters from Mr Dickens were found, there was no sign of a "Dickens dossier".

The investigation found that 114 potentially relevant files were not available, and were presumed "destroyed, missing or not found", although the independent investigator made clear that he found no evidence to suggest that the files had been removed or destroyed "inappropriately".

Lord Brittan welcomed the announcement of the Wanless probe, and said in a statement that allegations that he failed to deal adequately with Mr Dickens's allegations as home secretary were "completely without foundation".

Mrs May said that the independent inquiry panel will be made up of experts in the law and child protection, chaired by "an appropriately senior and experienced figure", with a remit to consider "whether public bodies - and other non-state institutions - have taken seriously their duty of care to protect children from sexual abuse".

She told MPs: "I want to be clear that the inquiry panel will have access to all the government papers, reviews and reports it needs. Subject to the constraints imposed by any criminal investigations, it will be free to call witnesses from organisations in the public sector, private sector and wider civil society.

"And I want to make clear that - if the inquiry panel chairman deems it necessary - the Government is prepared to convert it into a full public inquiry in line with the Inquiries Act."

Mrs May - who spoke to Mr Cameron about the child sex allegations on Sunday - made clear that the independent inquiry panel will look into failings by police, social services and schools in relation to abuse by celebrities like Jimmy Savile and Rolf Harris as well as the systematic abuse of vulnerable girls by gangs in cities like Derby, Rochdale and Oxford.

She indicated that the "non-state institutions" whose record on protecting children from abuse could include the BBC, churches and political parties.

"I think this has to be wide-ranging," Mrs May told MPs. "It has to look at every area where it is possible that people have been guilty of abuse and we need to learn lessons to ensure that the systems we have in place are able to identify that and deal with it appropriately."

She promised that the Government will do "everything we can" to allow the prosecution of abusers and to learn lessons from any past failings and will take an approach of "maximum transparency" in making information public.

Speaking ahead of Mrs May's announcement, Mr Cameron said: "I am absolutely determined that we are going to get to the bottom of these allegations and we're going to leave no stone unturned to find out the truth about what happened - that is vital.

"It is also vital we learn the lessons right across the board from these things that have gone wrong.

"And it's also important that the police feel that they can go wherever the evidence leads and they can make all the appropriate arrangements to investigate these things properly."

Rochdale MP Simon Danczuk, whose questions in Parliament last week about the Dickens' dossier fuelled pressure for an inquiry, welcomed Mrs May's announcement.

"I am pleased the Government has shifted its position significantly in the last few days and announced a Hillsborough-style inquiry," said Mr Danczuk. "This is the right thing to do and I welcome the fact that the Home Secretary has recognised the public mood and acted accordingly.

"Of course, the devil will be in the detail and I hope that the inquiry will have powers to hold the intelligence services and special branch to account where investigations into powerful child abusers have been discontinued or blocked... I also hope it will give an amnesty for retired and serving officers to give evidence on what they know about establishment paedophiles without fear of losing their pension or other repercussions."

For Labour, s hadow home secretary Yvette Cooper welcomed Mrs May's "changed position", saying: "Too often the system has failed young victims, not hearing them or believing them when they cried out for help and failing to protect them from those who sought to harm them.

"There have been particularly troubling cases of abuse involving powerful people and celebrities and the failures of institutions to act. When those allegations go to the heart of Whitehall or Westminster, as members from all sides of this House and all parties have made clear, it is even more important to demonstrate strong action will be taken to find out the truth and get justice for the victims involved.

Lawyer Alison Millar of Leigh Day, who represents alleged victims of a paedophile ring at the notorious Elm Guest House in south west London, said that the wide-ranging inquiry must approach the allegations "from the perspective of a survivor".

"Survivors must be provided with a safe environment in which to come forward with the correct support mechanisms, for them and their families," she said.

It was reported today that police have traced an alleged victim who has "implicated a senior political figure" in abuse at the Elm Guest House.

The man, who is now in his 40s and based in the US, has given a detailed account of how he was assaulted by the politician, but has so far refused to make a formal statement to detectives, said The Daily Telegraph.

The Home Office is also facing claims that a leading member of the notorious Paedophile Information Exchange (PIE) used its premises to store material.

According to the BBC, Steven Adrian Smith boasted in a little-seen book in 1986 that he had clearance to work as an electrical contractor at the Westminster building while chairman of PIE in the late 1970s and early 1980s, and hid files in locked cabinets there "where no police raid would ever have found them".

Mr Wanless said: "It's important to discover everything we can about what happened to these files, not only to help those who may have been victims of abuse many years ago but also to protect those children at risk now.

"The NSPCC is known for its independence and I will approach this review with the due diligence and dedication it warrants, which is what all children have every right to expect."

The chief executive of children's charity Barnardo's, Javed Khan, said: "There is much greater awareness of, and much less tolerance of child abuse now than there was 20 to 30 years ago.

"However, the outrageous failure of agencies to work together to protect children remains a serious problem and continues to lead to children being failed.

"The public need to be reassured that no-one is above the law when it comes to child abuse. Any allegations, whether they are current or historical, must be taken seriously and fully investigated by the police.

"Children who have suffered sexual abuse bear the emotional scars for the rest of their lives. Anyone who has used their power to escape punishment for committing sexual crimes against children must now be brought to justice.

"The inquiry announced this afternoon should not seek to duplicate the many current reviews under way. It should look at whether there are overarching lessons which can prevent similar abuses in the future."

Tory former MP David Mellor, who served under Lord Brittan as a Home Office minister in the 1980s, cast doubt on the quality of the evidence produced by Mr Dickens and called on people to "lay off" his former boss.

He said that while Mr Brittan had been "absolutely right" in what he did, the "fetid" atmosphere which had developed meant the inquiry was the right approach.

"Geoffrey Dickens came into the Home Office, he was seen by Leon Brittan and the information he had - which I very much doubt, knowing Geoffrey as well as I did, was a particularly carefully thought through set of representations - was then passed on to the relevant people within the department," he told Channel 4 News.

"People should lay off Leon Brittan. They should stop saying that Geoffrey Dickens somehow had the answer to life. Geoffrey didn't; he wasn't that kind of guy.

"He wasn't dissatisfied with Leon Brittan so why should anybody else be?"

He also hit out at former cabinet colleague Norman, now Lord, Tebbit for stating that there may well have been a cover-up.

"I don't know where Norman Tebbit was coming from. I know what he said deeply upset Leon Brittan and I'm not sure whether Norman, at this stage of his career, needs evidence to make these kind of headline-grabbing assertions.

"But the point is this review should be able to get to the bottom of this."

Former head of the civil service Lord Butler, who was principal private secretary to prime minister Margaret Thatcher at the time Mr Dickens submitted his claims, said he had not been aware of any rumours of a paedophile network at Westminster.

"I never heard anything about it at all," he told BBC2's Newsnight.

Given the number of files involved, he added, "it's quite difficult to imagine there could have been a cover up without quite a lot of people knowing about it".