Documents, believed to be genuine, were used by Jeremy Corbyn to lambast Tory party

An anonymous online poster who disseminated documents later brandished by Jeremy Corbyn as evidence the Conservatives would put the NHS “on the table” in US trade talks was part of a campaign directed by Moscow, the site hosting the papers has said.

On Friday evening, Reddit confirmed it has banned 61 accounts; including that of a user called Gregoriator, who it believes was part of a Russian information operation known as Secondary Infektion.

The anonymous user posted copies of the leaked official documents on the site in late October. Corbyn presented the same documents at a news conference last week, saying they “leave Boris Johnson’s denials [that the NHS would be for sale] in absolute tatters” and touting them as “evidence that, under Boris Johnson, the NHS is on the table and will be up for sale”.

Reddit insisted the post garnered minimal interest at the time and Labour has declined to reveal where it obtained the documents. The government has said it believes they are genuine.

However, questions will now be asked about whether Russia had a hand in introducing the papers into the UK’s public discourse and, if so, what its motivations were for doing so.

Nicky Morgan, the culture secretary, said it was “extremely serious” that the leaked documents could be linked to a Russian disinformation campaign. Speaking to BBC Radio 4’s Today programme on Saturday, Morgan said: “I understand from what was being put on that website, those who seem to know about these things say that it seems to have all the hallmarks of some form of interference.

“And if that is the case, that obviously is extremely serious. And actually as culture secretary, obviously one of the things that we are looking for and monitoring is any interference in our elections.”

The news also highlighted the vulnerability of the UK’s democratic processes to Moscow’s influence and will put pressure on Johnson over his refusal to release the parliamentary report into Russian meddling before the general election.

It led Dominic Grieve, the former chair of the parliamentary committee that put together the report, to renew his criticism of Johnson on Friday evening. He said it was “unfortunate” the document had been shelved for what he believed were “wholly dishonest” reasons and called for its publication.

Johnson has previously claimed there was insufficient time before the election but Grieve has pointed out the report had been signed off by the intelligence services and such documents are routinely published within significantly shorter timeframes.

Andy McDonald, the shadow transport secretary, renewed calls for the government to allow a report detailing Russian interference in UK elections to be published.

He said: “If we want to get to the bottom of the extent to which the Russian state interferes in elections, can we please publish the intelligence and security committee report? Let’s get that out there. That should have been published ages ago.”

On Monday, the social media research firm Graphika said that, while it could not definitively prove the Gregoriator account was controlled by Moscow, its methods closely resembled “techniques used by Secondary Infektion in the past, a known Russian operation”.

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It identified similarities, including grammatical errors in the early distribution of the documents via Reddit, three German-language websites and an anonymous Twitter account.

Secondary Infektion is the name given to a Russian operation exposed by Facebook earlier this year, operating across six languages and dozens of platforms. Subsequent analysis by the Atlantic Council, a US thinktank, demonstrated it was behind a string of largely failed attempts to disseminate fake news, including a blatantly false story that British remainers were planning to assassinate Johnson.

Announcing its move on Friday, Reddit said: “We were recently made aware of a post on Reddit that included leaked documents from the UK. We investigated this account and the accounts connected to it and today we believe this was part of a campaign that has been reported as originating from Russia.”

The site said it had found a “pattern of coordination” similar to that seen among social media accounts linked to Secondary Infektion, leading it to “use these accounts to identify additional suspect accounts that were part of the campaign on Reddit”.

A Labour spokesman said: “These documents reveal the plot against our NHS. And of course neither the UK nor the US government have denied their authenticity. Our releasing them to journalists was clearly in the public interest.”

The Conservatives have not responded to a request for comment.