"And now you come here for a press opportunity".
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Mr Johnson later tweeted: "I've been PM for 57 days, part of my job is to talk to people on the ground and listen to what they tell me about the big problems".
The PM claimed he was "here to find out" about hospital conditions but Mr Salem said: "It's a bit late isn't it?"
The angry father, who was standing opposite the Prime Minister in Whipps Cross Hospital, said the NHS is not receiving enough funding from the government and its current state is "unacceptable".
"The NHS has been destroyed", the father said as nearby cameras rolled.
The Prime Minister said the press was not present but Mr Salem pointed to the TV cameras. There are not enough doctors, nurses, it's not well organised enough.
"I think members of the public are becoming increasingly frustrated with photos and campaign visits when they want to see him sat down dealing with Brexit and other important issues".
Shadow health secretary Jonathan Ashworth said: "Boris Johnson simply can't be honest with people".
"If he'd been a Tory blue voting for ten years, if you'd a poor experience of your child in the NHS I'm pretty sure you'd feel the same way".
He told Johnson his young daughter had been neglected in the hospital overnight when she needed care.
Alan Gurney, Chief Executive of Whipps Cross hospital, said: "We are constantly reviewing staffing levels on our wards to ensure our patients are safe at all times".
A spokesman for Number 10 said the man was understandably "very distressed" and the Prime Minister was "not going to hide away from those circumstances when he goes on these visits, and so obviously is keen to talk to people and empathise and see what he can do to help".
A spokesman added: "This is why we've recently invested an additional £1.8bn into frontline services and are upgrading 20 hospitals across the country".