Boris Johnson was warned three times to wear a mask for his hospital visit, but still wandered around without one.
Hexham General Hospital chiefs told him before the trip masks must be worn in all areas to protect staff and patients.
But the PM ignored their pleas and took his face covering off in a corridor, sparking fury from onlookers and care staff.
Mr Johnson, who has faced claims he was in Northumberland – some 300 miles from Westminster – to dodge a debate in parliament on Tory sleaze, was swiftly “given a mask and he put it on.”
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A new statement released by the hospital casts doubt on Downing Street’s claims that the PM followed the rules.
Sources have also confirmed to the Mirror, however, that No10 was “formally advised” via email and “reminded” of face covering rules by medics when he arrived on on Monday.
“I am confident he will have been abiding by the rules in place,” No10 said on Monday.
And at the time, the hospital said he had obeyed rules “in each clinical area he visited”.
Susie Flintham, of the campaign group Covid-19 Families for Justice, said: “I lost my father, Howard, after he caught Covid-19 in hospital, and there are over 11,000 of us who lost loved ones in the same way. One of the main reasons for this was frontline NHS workers not having access to masks and other PPE.
“By visiting a hospital and refusing to put his mask on, despite being repeatedly asked to, the Prime Minister was putting lives at risk completely unnecessarily. For him to make a point of posing for a photo without a mask, at a time when Covid cases are at their highest level since February, is a slap in the face to bereaved families. What on earth was he hoping to achieve? Has he learnt nothing from the pandemic?
“It feels like the Prime Minister is determined to make us feel like he doesn’t have to play by the rules that we do. Or that he doesn’t care that his actions are putting people at risk. It’s like he wants to rub it in the faces of grieving families.”
Hospital insiders had also claimed that No 10 had asked them not to comment to the press after the photo of the PM not wearing a mask emerged.
Wansbeck MP Ian Lavery, whose constituents are served by the hospital, said: “People were astonished to see this happen – that the Prime Minister of the country was bowling up the corridor of an NHS hospital without a mask on.
“This shows a callous disregard for the patients, the visitors and the fantastic workforce, who have been at the frontline throughout the pandemic.”
It is understood staff e-mailed the PM’s team with advice on mask-wearing, which says face coverings should be worn in all areas of the hospital.
A staff member reminded Mr Johnson of the rules when he arrived – and he was then reminded a third time after he briefly took his covering off.
It comes after the Prime Minister was pictured without a mask next to 95-year-old national treasure Sir David Attenborough at the COP26 summit.
Some other photos from the same event in Glasgow did show Mr Johnson wearing a face covering.
Bosses at Northumbria Healthcare NHS Foundation Trust issued the information as it “apologised for any upset” after complaints by the public.
They said: “Our mask-wearing rules are very clear, and it is important to note that everyone that was part of the official visit to Hexham General Hospital on Monday 8 November were formally advised and reminded of these rules on the day.
“Information was included in the written programme.
“These rules include information about mask-wearing and other infection prevention and control measures, such as hand-washing, tucking away loose clothing (ties), and having rolled-up sleeves.
“After the Prime Minister left a welcome meeting, he walked along a mezzanine corridor, for a very short period of time, without a mask.
“This brief moment was captured on camera. As soon as this was identified he was given a mask and he put it on.
“The Prime Minister did wear a mask for the majority of the visit. He didn’t have a mask on when he did his media interviews, but this was with agreement with everyone else in the room, who did wear a mask.”
The Mirror has approached Downing Street.