More than four million people stopped wearing face coverings in public this summer, official figures have revealed as a senior government scientific adviser warned Tuesday’s maskless cabinet meeting would be “toxic” to already falling public adherence to guidance.

Use of face coverings has been dropping since its peak at the beginning of May, when 98% of people said they had worn one in the past week when leaving the house. That dipped to 89% this month, implying 4.5 million people in Great Britain stopped wearing masks at all, Office for National Statistics data showed.

ONS does not gather data on regular mask-wearers, whose numbers will be lower. YouGov asked if people had “worn a face mask when in public places” in the past fortnight and found only 61% said yes, a fall of 10 percentage points from mid July to 9 September.

In London, where masks remain mandatory on Transport for London services, compliance was at about 82% in August, implying hundreds of thousands of people are not wearing masks. However, officers had excluded only 221 people from using services and directed 53 to leave in the seven weeks since 19 July, when wider UK law on masks changed and passengers no longer faced the threat of prosecution.

Finn Brennan, an organiser for the trade union Aslef, said there were “fewer and fewer people wearing masks and … no obvious sign of enforcement … staff are feeling much more at risk”. Train passengers have also complained of patchy usage.

Behavioural scientists and Covid bereaved this week voiced anger at the message sent by images of Boris Johnson and his cabinet gathering closely around the cabinet table without masks, as average weekly fatalities from Covid rose to the highest level since March.

Rules requiring masks in shops, restaurants, on public transport and in other confined public spaces in England were dropped on 19 July, but the government’s Covid winter plan suggests people “wear a face covering in crowded and enclosed settings”. Large numbers of MPs have also been seen in the House of Commons chamber not wearing face coverings.

Prof Stephen Reicher, a member of the Sage subcommittee advising on behavioural science and a psychologist at the University of St Andrews, said images of a meeting of maskless cabinet ministers appearing to disregard their own advice could be “truly toxic” for public trust and adherence.

“Messaging is not only what you say, it’s what you do and what your policies convey,” he said. “If those images create that sense of ‘them and us’, which I think they pretty clearly do, it is a very caustic thing.”

Lobby Akinnola, who lost his father to Covid in the first wave and helps organise the Covid-19 Bereaved Families for Justice group, which is calling for an urgent public inquiry, said: “Many of us that have lost loved ones are extremely distressed to see packed train carriages, parliamentary chambers and indoor spaces with very few masks in sight.

“The government has always claimed to be following the science so why is it now ignoring the advice of Sage?”

David Heymann, a professor of infectious disease epidemiology at the London School of Hygiene & Tropical Medicine and head of the Centre on Global Health Security at Chatham House, said: “Masks are a precautionary measure and we should be willing to use precautionary measures if there’s any evidence that it’s useful. The rule is: if you can’t physically distance, you should wear a mask.”

Lyn Jones, 69, whose husband, Gareth, died of Covid on 1 March this year, has been confined to bed with Covid in recent days and said mask-wearing must become mandatory again.

“My husband would be here if we had proper lockdowns before Christmas and again they are trying to appeal to people by saying you don’t have to wear a mask when it is the simplest thing to do,” she said. “I am angry about it all. What an example when they were all in the Cabinet meeting with no masks on. I caught this since ‘freedom day’ and it doesn’t feel like freedom when you can’t get out of bed.”