A World Health Organisation (WHO) chief has called on all world leaders, including Boris Johnson, to wear a face mask in indoor settings.
It comes amid criticism of Mr Johnson after he was this week photographed maskless during a hospital visit.
The Prime Minister was seen walking along a corridor in Hexham General Hospital in Northumberland and posing for pictures alongside medical staff who donned light blue face coverings.
Mr Johnson was seen elbow-bumping and wearing a mask at some other points.
Dr David Nabarro, WHO special envoy for Covid-19, urged all world leaders to wear face masks in a bid to reduce transmission.
He told Sky News: “I’m not sitting on the fence on this one - where you’ve got large amounts of virus being transmitted, everybody should do everything to avoid either getting the virus or inadvertently passing it on.
“We know that wearing a face mask reduces the risk, we know that maintaining physical distance reduces the risk, we know that hygiene by regular hand washing and coughing into your elbow reduces the risk.
“We should do it all and we should not rely on any one intervention like vaccination on its own.
“So, please, would every leader be wearing face masks? Particularly when in indoor settings.”
Dr Narbarro added: “This virus is unforgiving and we need to do everything possible to prevent it getting in between us and infecting us.”
He also expressed frustrations that responses to the pandemic have been “politicised”, telling the broadcaster: “Perhaps that’s the toughest thing about Covid is that the responses get politicised - in some places if you wear a mask, you’re taught to belong to a particular political party.
“That’s the most regretful thing about the present situation, we all need to be able to do what we’ve got to do, regardless of what politics we adopt.”
No 10 said the Prime Minister had followed the guidelines set by the local NHS trust.
