Video report by ITV News Political Correspondent Carl Dinnen
The Labour leader held up classified documents during the campaign which detailed trade talks between the US and UK which he said were part of "secret talks" to sell off the NHS.
Mr Johnson described the reports as "nonsense" while Labour said the document proves that the Tories are willing to privatise parts of the NHS in order to secure a trade deal with the US.
The document was first shared on Reddit in October and the website said it believes it is "part of a campaign that has been reported as originating from Russia".
Reddit said it had closed one subreddit stream - a chat forum where people are discuss topics on a certain subject - while 61 accounts were also closed for "vote manipulation and misuse of the platform".
The website added the accounts "have shared the same pattern" as a Russian campaign found earlier on Facebook this year, called "Secondary Infektion".
In a statement, Reddit said: "Suspect accounts on Reddit were recently reported to us, along with indicators from law enforcement, and we were able to confirm that they did indeed show a pattern of coordination.
"We were then able to use these accounts to identify additional suspect accounts that were part of the campaign on Reddit.
"This group provides us with important attribution for the recent posting of the leaked UK documents, as well as insights into how adversaries are adapting their tactics."
Labour has refused to disclose where it obtained the sensitive documents, but noted that the veracity of the paper had not been dismissed by either the US or UK government.
A Labour spokesperson 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."
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."
Culture Secretary Nicky Morgan said it was "extremely serious" that the leaked documents could be part of a Russian interference in the general election.
She told BBC Radio 4's Today programme: "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."