Omar Salem, whose week-old daughter was being treated at Whipps Cross University Hospital in east London, told the prime minister during a hospital visit on Wednesday: “The NHS has been destroyed...and now you come here for a press opportunity.”
In a heated two-minute exchange, the father claimed there had been “years and years and years of the NHS being destroyed” and told Mr Johnson it was “not acceptable”.
He added: “There are not enough people on this ward, there are not enough doctors, there’s not enough nurses, it’s not well organised enough.”
Mr Johnson said “there’s no press here” but the parent gestured to cameras filming the confrontation and said: “What do you mean there’s no press here, who are these people?”
After pictures emerged of the confrontation, Mr Salem tweeted: “Boris Johnson had the temerity to come to Whipps Cross Hospital for a press opportunity on the children’s ward that my 7 day old daughter is on, having been admitted to A&E yesterday gravely ill.
“The A&E team were great but she then went for hours on the ward without seeing a doctor.”
BBC political editor Laura Kuenssberg also retweeted Mr Salem’s post, adding: “This is him here.”
Once his identity, and the fact he referred to himself a Labour activist, was revealed, the father was met with a barrage of abuse.
One Twitter user wrote: “A left wing labour activist using their child as a political football. Not to mention riding the NHS as usual. Shameful and predictable.”
While another said: “There’s no mitigating the pain of a parent with a sick child but the media failed to tell you that the heckler who shouted at Boris in a hospital today is a Labour Party activist who worked for Emily Thornberry.”
One person claimed the father was “a Labour activist who used his daughter in a cheap political stunt,” adding: “Hardly parent of the year stuff.”
Some also claimed the confrontation was “staged” and a “political stunt”, with one saying: “Another lefty remainer. Boris stop letting the traitors keep setting you up.”
However many people leapt to Mr Salem’s defence, saying his political views were irrelevant and that he was speaking as a father concerned for his daughter.
“ITV mentioned he was a Labour activist...but he was there as a father of a [week-old] child fighting for its life,” said one person.
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While another Twitter user added: “His child was sick that is why he was in the hospital and he did not arrange the press as press followed Johnson. Besides what this man said was true.”
Some were also critical of Ms Kuenssberg’s sharing of the tweet, arguing that it helped facilitate the abuse.
“You need to delete this and then apologise. At best this shows poor judgement. Your job is to report the news as fairly as you can, not to provoke a Twitter mob,” said one user.
“BBC staff facilitating dogpiling the day after hosting an anti trolling programme,” said another.
BBC later published a statement in response, saying that Ms Kuenssberg’s use of social media is “part of her job.”
“Any suggestion that there was malicious intent behind her tweet is absurd.”