The VIP paedophile scandal deepened last night after it emerged that an MP suspected of child abuse was let off the hook by the security services.

Newly released papers reveal that in 1986 the then director general of MI5, Sir Antony Duff, looked at claims that the MP ‘has a penchant for small boys’.

But the inquiry was dropped when the security services simply accepted the MP’s claims that the allegations were false.

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The men include former Home Secretary Leon Brittan (pictured), ex-diplomat Sir Peter Hayman, former minister Sir William van Straubenzee and Sir Peter Morrison, who was an aide to Margaret Thatcher

Shockingly, Sir Antony concluded: ‘The risks of political embarrassment to the Government is rather greater than the security danger.’

The MP in question was not named in the explosive document, which was among several papers released last night by the Home Office after a request by Sky News.

The other files related to a series of Westminster figures from the 1970s and 1980s – Margaret Thatcher’s former parliamentary secretary Sir Peter Morrison, former Home Secretary Leon Brittan, former diplomat Sir Peter Hayman and former minister Sir William van Straubenzee. All are now dead.

The contents of the documents were not revealed. But they have been shared with the police and will be passed to the Child Abuse Inquiry led by Justice Lowell Goddard.

Earlier this year the Government was forced to release the details of a file prepared for Mrs Thatcher’s office on the ‘unnatural sexual’ behaviour of Sir Peter Hayman, who worked for MI6. The new batch of files reveal there were further Government papers relating to him.

Last year a review by NSPCC chief executive Peter Wanless and barrister Richard Whittam, QC, failed to find many of the relevant abuse files held by Government departments.

Sir Peter Morrison (left) and Sir Peter Hayman (right) have been named among the senior Westminster figures

It emerged last night that further searches had uncovered a number of other relevant letters dating from the 1980s. Some of them contained references to the Kincora Boys’ Home in Northern Ireland, which has been at the centre of VIP paedophile allegations.

The Cabinet Office has since apologised to Mr Wanless and Mr Whittam for failing to ‘identify the papers in question when you first asked for them’. Last night in a supplement to their report the authors said they did not believe files had been deliberately suppressed.

Former Tory MP for Wokingham, Sir William van Straubenzee (pictured), who died in 1999, is also among the key figures named today

But they said there were shocking incidents where it was clear cases of child abuse were not taken as seriously in the 1980s as now.

‘There were a number of references across the papers we saw that reinforced the observation we made in our review that issues of crimes against children, particularly the rights of the complainant, were given considerably less consideration than would be expected today,’ they said.

‘To give one striking example, in response to claims from two sources that a named MP “has a penchant for small boys”, matters conclude with acceptance of his word that he does not and the observation that “at the present stage, the risks of political embarrassment to the Government is rather greater than the security danger”. The risk to children is not considered at all.’

The letter in question was written by MI5’s Sir Antony to Sir Robert Armstrong, the Cabinet Secretary, on November 4, 1986.

Last year’s review by Mr Wanless and Mr Whittam of the Home Office’s handling of allegations concerning a paedophile ring in the 1970s, 1980s and 1990s found no evidence of a cover-up.

Fresh allegations about Lord Brittan emerged this week when he was named by an alleged abuse victim on Australian TV show 60 minutes. The man claimed that, like late Liberal MP Cyril Smith, Lord Brittan was a regular visitor to paedophile parties at Dolphin Square in Pimlico, central London.

Last night Labour MP John Mann said the new files showed there had been a cover-up. He added: ‘There was no interest in dealing with the abuse of children. There needs to be an investigation into why MI5 were failing to act.’