Less than half of young people are now wearing face masks in public places, a YouGov poll suggests, but eight out of 10 over-65s are continuing to use them.
The survey suggests the use of face masks among 18 to 24-year-olds has slumped since July 19, with around 46 per cent saying they wore one in a public place in the last two weeks, compared to 58 per cent on July 16 and 64 per cent on June 2.
It is the lowest level of mask use since July last year, when 42 per cent of that age group said they were wearing them.
Meanwhile, the survey of 1,742 British adults between July 21 and 22 found other age groups were still wearing face coverings at around the same rate.
Sixty-nine per cent of all Britons said they wore a mask in the last two weeks, compared to 71 per cent on July 16 and 73 per cent on June 2. Among over-65s, 83 per cent said they were still wearing one in public places.
YouGov also said young people were less likely to be fully vaccinated and more likely to have disabled their NHS Covid app.
But one government adviser said public behaviour had changed more "gradually" and "cautiously" than expected after "Freedom Day".
Sir Jeremy Farrar, the director of the Wellcome Trust and a member of Sage, said Britain should "celebrate" the reduction in cases in recent days, but added that it was too early to tell whether July 19 has had an impact.
"I think people’s behaviour has changed, to take Chris Whitty’s advice, much more gradually and much more cautiously than perhaps anybody could have imagined 10 days ago," he said.
"I would hope that therefore we will not see a massive rebound if we continue to be gradual and cautious about what we do."