Leaked documents cited by Jeremy Corbyn are tied to a previous Russian disinformation campaign, according to internet discussion site Reddit.
The Labour leader used the classified documents detailing trade talks between US and UK officials as evidence of what he said is a plot to sell off the NHS.
"The uncensored documents leave Boris Johnson's denials in absolute tatters," Mr Corbyn told a news conference last week.
The prime minister dismissed the claims as "total nonsense" and his party said the Labour leader had misrepresented the documents and quoted sections out of context.
The documents first appeared in a post on Reddit in October and the site has now said it believes it is "part of a campaign that has been reported as originating from Russia".
It said it had also identified more accounts which had used "vote manipulation" to promote the original post.
Reddit said the accounts "have the same shared pattern" as a Russian campaign found on Facebook earlier this year, dubbed "Secondary Infektion".
The site has banned one subreddit and 61 accounts "under our policies against vote manipulation and misuse of the platform".
Sky's technology correspondent Rowland Manthorpe says it is not known if the leaked documents were hacked or obtained by the Russian group - only that they were trying to "amplify" their visibility.
He said what the Russians have been doing "isn't disinformation, because so far as we know the documents are legit".
Manthorpe added: "Labour needs to take this seriously - because, however tenuously, this is increasingly looking like foreign interference in the UK election."
The Facebook campaign this Reddit effort resembles was called Sekondary Infektion after the original Infektion, a Russian disinformation campaign from the 1980s
It was devoted to planting the idea the US invented HIV/AIDS as part of a biological weapons research project— Rowland Manthorpe (@rowlsmanthorpe) December 6, 2019
A government spokesperson said: "Online platforms should take responsibility for content posted on them, and we welcome the action Reddit have taken today.
"The UK government was already looking into the matter, with support from the National Cyber Security Centre (NCSC).
"We do not comment on leaks, and it would be inappropriate to comment further."