Boris Johnson has said an investigation is needed into the source of leaked documents on UK-US trade negotiations posted on Reddit. Labour says the documents show the NHS would be at risk under a post-Brexit trade deal with the US. On Friday, forum website Reddit said unredacted documents were uploaded as “part of a campaign that has been reported as originating from Russia”. It has suspended 61 accounts that showed a “pattern of coordination”. The government said it was looking into the matter with help from the National Cyber Security Centre. Speaking on Saturday, Mr Johnson said “we do need to get to the bottom” of the leak but said he had seen “no evidence of any successful interference by Russia in any democratic event in this country”. The Culture Secretary Nicky Morgan said this all pointed towards foreign involvement: “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.” Labour’s shadow transport secretary Andy McDonald reiterated his call for Mr Johnson to release an intelligence report into Russian covert actions in the UK, which No 10 has been accused of suppressing until after the election. In a post on its site, Reddit did not provide any further details about the evidence behind its conclusions, nor did it identify any specific individuals. The BBC has approached the Russian foreign ministry spokesperson but they have yet to comment. The contents of the documents have played a significant part in Labour’s election message on the NHS, after Mr Corbyn highlighted them at a press conference on 27 November. The Labour leader said the papers were evidence that the UK government was in advanced stages of negotiations with the US to open up the NHS to American pharmaceutical companies A bit like journalists never reveal their sources, Labour are quite happy to focus on what these documents say rather than where they come from. We’re still talking about these documents and what Labour claims that they show – that the NHS is up for sale, in their words. Boris Johnson and the Conservatives flatly deny that. Speaking on Saturday, the Labour leader said the controversy surrounding the source of the documents was “nonsense” and accused Mr Johnson of wanting to “hide the issues and the truth” over the future of the NHS in trade deals. Neither UK nor US governments have disputed the authenticity of the documents.