A member of the public has claimed she has suffered death threats after being named online as the source of a false claim that the photo of a sick four-year-old boy on a hospital floor was staged.

The woman is alleged to have posted the claim on Facebook, which has now gone viral.

The development came after the editorial director of the Yorkshire Evening Post, which broke the story, attacked "dark forces" for attempting to discredit it online.

The newspaper first reported the story of Jack Williment-Barr after his mother Sarah Williment covered him in coats to keep him warm on the floor of Leeds General Infirmary, where he lay for more than four hours awaiting treatment for suspected pneumonia. After five more hours on a trolley Jack was diagnosed at three in the morning with flu and tonsillitis and later went home.

The incident has dominated the last 24 hours of the election campaign given the row that ensured following Boris Johnson’s initial refusal to look at the photo of Jack when it was shown to him by ITV journalist Joe Pike.

However, later on Monday, hundreds of duplicated messages began to appear from various accounts on Facebook and Twitter, attempting to debunk the photo’s veracity.

The copied and pasted message read: "Very interesting. A good friend of mine is a senior nursing sister at Leeds Hospital - the boy shown on the floor by the media was in fact put there by his mother who then took photos on her mobile phone and uploaded it to media outlets before he climbed back onto his trolley."

The original message was attributed by social media users to a Facebook post by a member of the public.

After a reader contacted him about the claim, James Mitchinson, Johnston Press' editorial director for Yorkshire, tweeted a letter he had sent her outlining the newspaper's processes for verifying the story.

He added the newspaper "went to great lengths to establish the story was true", adding: "I would be happy to meet you over a coffee to offer you an explanation as to how sophisticated and corrosive the proliferation of fake news is and what to do to guard against being conned by it.

"I do hope we are not too late to help people like her, so unfairly manipulated and discombobulated by cynical social media messaging driven by dark forces," he said.

While it is difficult to verify the original source of the attempts to discredit the photo, researchers at anti-disinformation group First Draft found several hundred copies of the message across Facebook and Twitter, including shares by prominent celebrities and journalists.

Alastair Reid, digital editor at First Draft, said: "Both on Facebook and Twitter we've seen a concerted effort to put this claim in front of as many people as possible.

"On Twitter that has meant accounts have been contacting celebrities, athletes, journalists and politicians and telling them to share it. On Facebook we have seen the same paragraph of text pushed into pro-Brexit and pro-Conservative Facebook groups again and again and again."

However, he urged people to steer clear of talk of "bots" - or automated accounts - driving the conversation.

"At this stage it's very difficult to say whether there is any automated or co-ordinated activity and it's better not to jump to conclusions," he added.