The security services are facing questions over the cover-up of a Westminster paedophile ring as it emerged that files relating to official requests for media blackouts in the early 1980s were destroyed.

Two newspaper executives have told the Observer that their publications were issued with D-notices – warnings not to publish intelligence that might damage national security – when they sought to report on allegations of a powerful group of men engaging in child sex abuse in 1984. One executive said he had been accosted in his office by 15 uniformed and two non-uniformed police over a dossier on Westminster paedophiles passed to him by the former Labour cabinet minister Barbara Castle.

The other said that his newspaper had received a D-notice when a reporter sought to write about a police investigation into Elm Guest House, in southwest London, where a group of high-profile paedophiles was said to have operated and may have killed a child. Now it has emerged that these claims are impossible to verify or discount because the D-notice archives for that period “are not complete”.

Officials running the D-notice system, which works closely with MI5 and MI6 and the Ministry of Defence, said that files “going back beyond 20 years are not complete because files are reviewed and correspondence of a routine nature with no historical significance destroyed”.

The spokesman added: “I cannot believe that past D-notice secretaries would have countenanced the destruction of any key documents. I can only repeat that while any attempted cover-up of this incident might have been attributed to a D-notice the truth would be that it was not.”

Theresa May, home secretary, this month told the Commons that an official review into whether there had been a cover-up of the Home Office’s handling of child-abuse allegations in the 1980s had returned a verdict of “not proven”. The review, by Peter Wanless, the chief executive of the National Society for the Prevention of Cruelty to Children, was prompted by the discovery that 114 Home Office files related to child abuse in the 1980s had gone missing.

On Saturday night the Labour MP for Rochdale, Simon Danczuk, whose book Smile for the Camera exposed the child sex abuse of the late Liberal MP Cyril Smith, said it was a matter of deep concern that D-notice correspondence had also disappeared, presumed destroyed. D-notices to media outlets are rare, with just five sent in 2009 and 10 in 2010, according to a freedom of information response from Air Vice-Marshal Andrew Vallance, secretary of the defence, press and broadcasting advisory committee, which oversees the system.

Danczuk said: “There are clearly questions to be answered as to why these documents were destroyed. They issue very few of them – where was the need to destroy correspondence?

“It feels like just another example of key documents from that period going missing. We need to know more about what has happened. The journalists who have said that D-notices were issued are respected people with no reason to lie.”

The two journalists, Don Hale, the former editor of the Bury Messenger, and Hilton Tims, news editor of the Surrey Comet between 1980 and 1988, both recall their publications being issued with D-notices around 1984. Tims, a veteran of the Daily Mail and BBC, where he was head of publicity for the launch of colour TV, said that his chief reporter had informed him that a D-notice had been issued to him after he tried to report on a police investigation into events at Elm Guest House, where Smith is said to have been a regular visitor.

Tims, 82, said: “One of the reporters on routine calls to the police learned that there was something going down at the guest house in Barnes. It was paedophilia, although that wasn’t the fashionable phrase at the time, it was ‘knocking up young boys’, or something like that.

“The reporter was told that there were a number of high-profile people involved and they were getting boys from a care home in the Richmond area. So I put someone on to it, the chief reporter I think, to make inquiries. It was the following day that we had a D-notice slapped on us; the reporter came over and told me. It was the only time in my career.”

Hale, who was awarded an OBE for his successful campaign to overturn the murder conviction of Stephen Downing, a victim of one of the longest-known miscarriages of justice, said he was issued with a D-notice when editor of the Bury Messenger. He had been given a file by Castle, by then an MEP, which had details of a Home Office investigation into allegations made by the Tory MP Geoffrey Dickens of the existence of a Westminster paedophile ring. The files contained the name of 16 MPs said to be involved and another 40 who were supportive of the goals of the Paedophile Information Exchange, which sought to reduce the age of consent.

Hale said he asked the Home Office for guidance on the dossier and the progress of the investigation but was stonewalled.

Hale said: “Then shortly after Cyril Smith bullied his way into my office. I thought he was going to punch me. He was sweating and aggressive and wanted to take the files away, saying it was a load of nonsense and that Barbara Castle just had a bee in her bonnet about homosexuals. I refused to give him the files.

“The very next day two non-uniformed officers, about 15 uniformed officers and another non-uniformed person, who didn’t introduce himself, came to the office waving a D-notice and said that I would be damaging national security if I reported on the file.”

A spokesman for the D-notice system said: “If Don Hale was ‘served’ with anything purporting to be a ‘D-notice’, it was quite obviously a fabrication.”