Boris Johnson has finally apologised for failing to wear a mask on a recent hospital visit – despite No 10 having claimed he followed the rules at all times.

The prime minister conceded he was at fault when he walked the corridors in Hexham Hospital, after reports he was warned three times to put on the face covering.

But he told MPs the incident should not be added to his “litany of crimes”, saying: “There were barely 30 seconds when I wasn’t wearing a mask.

“I walked out of the room mistakenly not wearing it. I put it on as soon as I realised I had made the mistake. I apologise for that.”

Speaking to a committee of MPs, the prime minister insisted that “most pictures of my visit to the hospital” would show him wearing a face covering.

Mr Johnson was accused of a disregard for the NHS and Covid, after hospital chiefs emailed Downing Street before the visit – eight days ago – insisting masks must be worn in all areas.

The prime minister’s team was reportedly reminded of the rules when he arrived, but he took off his mask as he walked along a corridor and met staff.

The hospital trust’s website stated: “You must ensure that you wear your covering or mask throughout your visit,” adding that the rules applied to everyone and all parts of the premises.

The apology came despite Ms Johnson’s notorious refusal to apologise for other mistakes – including the botched attempt to fix anti-sleaze rules to clear Owen Paterson.

It also follows the refusal, until recently, of Tory MPs to wear masks in the crowded Commons chamber – despite rising Covid infection rates at Westminster.

The failure to wear a mask kicked off a controversy in the north east. One local Labour MP, Ian Lavery, said: “People were astonished that the prime minister was bowling up the corridor of a hospital without a mask.

“This shows a callous disregard for patients, visitors and the fantastic workforce, who have been at the frontline throughout the pandemic.”

Susie Flintham of the campaign group Covid-19 Families for Justice said: “The PM was putting lives at risk completely unnecessarily by visiting a hospital and refusing to put his mask on, despite being repeatedly asked to.

“For him to make a point of posing for a photo without a mask is a slap in the face to bereaved families.”

The prime minister faced similar criticism at the Cop26 climate summit for being pictured next to 95-year-old David Attenborough while not wearing a mask.