Chief MedicalOofficer Chris Whitty speaking at the media briefing in Downing Street today – Image: PA

Despite official government advice, the Mayor of London Sadiq Khan wants people in the capital to wear facemasks when outside, saying they are an effective way of slowing coronavirus transmission.

Mirror Online reports: “The Mayor of London has said he believes the public should be wearing facemasks when they leave the house – just hours after the government’s top science advisor told journalists their effectiveness was minimal.

“Sadiq Khan said he had asked the UK government to encourage people to wear face coverings, but that they hadn’t changed the advice.”

Speaking on BBC London Mayor Khan said: “I’m hopeful that the advice from the scientists will change.

“The evidence around the world is that this is effective. I am lobbying our government and our advisers to change their advice and I want us to do that sooner rather than later.”

Face  coverings – like cloth masks – are different from the medical equipment required by the NHS as PPE and so would not compete for the same supply, the report added.

“Earlier this evening, UK chief medical officer Chris Whitty told the daily coronavirus news conference at Downing Street that whether the British public should wear face masks to protect against Coronavirus was “a very live issue”.

The government’s top science advisor said that evidence of their effectiveness was minimal.

“The evidence is weak, but the evidence of a very small effect is there under certain circumstances,”  he said.

Existing official advice is that masks are not necessary for the public while outside.

The World Health Organisation recently reiterated that the face coverings “should be saved for those in health and care who really need them,” Health Secretary Matt Hancock stressed last Friday.

And the organisation’s official advice says: “If you are healthy, you only need to wear a mask if you are taking care of a person with a suspected Covid-19 infection.”  

But today Professor Whitty was challenged by a question from a reporter to “illuminate how you reached the Government line that masks are no help outside of a care setting”.

“The question came in the light of challenges to the Government’s position by University of San Francisco data scientist Jeremy Howard and former Health Secretary Jeremy Hunt.

“Professor Howard, the founder of the #Masks4All campaign, led a review panel with 18 other experts from around the globe and found ‘substantial evidence in favour of widespread mask use to reduce community transmission’.

“Mr Howard cited the WHO’s assistant director-general David Heymann’s comment that masks were equally or more effective in combating the spread of Covid-19 than social distancing, and said the situation in Taiwan provided further proof.”

He told ITV’s Peston programme: “Regardless of how you look at it, it looks like there’s an extra 1,500 deaths a week (in the UK) due to this disease.

“The entire country of Taiwan has five deaths. Now here’s an example of a great country that is distributing masks to everybody.”

Mr Hunt has suggested that face masks could reduce the spread of the virus on the London Underground once people return to work following the lockdown.

Prof Whitty was also today asked whether the Government came to is conclusion by considering only the medical evidence about transmission or was it “also taking into account the obvious fact that there aren’t enough masks to go around to the general public?”

Prof Whitty said: “Well it is certainly the case that if there was ever a competition between health care workers and care workers in the front line, and people using them in situations where the risk is incredibly low, I don’t think it takes a scientist or a doctor to work out that would be a very bad thing to happen.

“And that’s one of the reasons why the World Health Organisation reiterated its advice that, in most settings, masks should be for healthcare workers.

“However this is a very live issue that we are re-examining and [Government advisory group] SAGE – which Patrick [chief scientific adviser Sir Patrick Vallance] chairs – re-looked at that this morning and other scientific groups are re-looking at the evidence.

“I think my summary to date would be; the evidence is weak, but the evidence of a very small effect is there under certain circumstances, and what we’re really trying to do is work out under what circumstances, if any, should we extend the advice and under what circumstances should we not change that advice.

“But the point  about scientific advice is it evolves, and that is one of the things that we have to do the whole time, is to re-examine evidence as it comes in and that’s the reason SAGE has looked at it and why we’ve looked at it in other scientific settings,” he added.

Meanwhile, Deputy Chief Medical Officer Jonathan Van-Tam said on Friday that NERVTAG had met last week and remained “convinced that there just isn’t the evidence base to support general mask wearing use by the public”.