The MI5 security service pushed for a cover-up of child abuse allegations against Peter Morrison, according to Whitehall files.
Morrison was a Tory MP and aide to then prime minister Margaret Thatcher.
A key paper from November 1986 shows Sir Antony Duff, then director general of MI5, writing to cabinet secretary Robert Armstrong, who is now a Lord.
It referred to inquiries into an MP said to have “a penchant for small boys”.
The MI5 chief added, “At the present stage the risks of political embarrassment to the Government is rather greater than the security danger”.
The Duff note was disclosed to Peter Wanless, head of the NSPCC charity, and Richard Whittam QC, who published a review last year.
It was supposed to bring to light all the apparently missing documents over the abuse scandals.
However a series of documents have now emerged that were previously thought to be lost or destroyed.
Wanless and Whittam said Sir Antony’s words are a “striking example” of how “the risk to children is not considered at all”.
One of Morrison’s victims said earlier this year, “He’d leave me alone for a little bit, and then he’d come at me again. Before long, he had my trousers off.
“At one point we stopped for petrol, and I thought about running out of the car, but I realised the doors had some sort of child lock and I couldn’t get out.
“I was so frightened. It was the most horrendous experience of my life.”
Morrison took the boy to a house, probably Elm Guest house in Richmond, in 1982. He raped the boy. The boy escaped and reported the attack to the police.
A year later the police returned his clothes and said a man had been convicted and sentenced to two years in prison. It was a lie.
The papers include documents and correspondence relating to senior Westminster figures.
They include Morrison, former home secretary Leon Brittan and Sir William van Straubenzee, former Tory Northern Ireland minister. All three are dead.
The documents have not been disclosed but a description of them has. In them is a file referring to the security risks posed by the “unnatural sexual proclivities” of diplomat and deputy director of MI6 Sir Peter Hayman.
Other papers relate to former head of MI5 and MI6 Sir Maurice Oldfield and his alleged connection to the Kincora boys’ home in Northern Ireland (see box).
Abuse victims say Oldfield visited Kincora.
The newly discovered files will be passed to the Goddard public inquiry into institutional abuse. The files were released on the day parliament closed for the summer.
Kincora probe blocked
Three workers at the Kincora boy’s home were convicted in 1981 of sexually abusing children there in the 1970s.
Yet British establishment figures, including senior politicians, were also involved.
The security services knew about the abuse but did nothing to stop it.
The papers included a file about former Northern Ireland minister Sir William Van Straubenzee, which “contained references to the Kincora boys’ home”.
Another group of papers contain allegations made by former military intelligence officer Colin Wallace. Successive governments denied receiving the allegations.
Wallace told his superiors what was happening and put out a press release as early as 1973. Yet Kincora is excluded from the child abuse public inquiry.