The mayor of Greater Manchester has called on supermarkets to hire more security staff to enforce mask wearing as the region continues to face tougher coronavirus restrictions.
Andy Burnham said he believed it was a "proportionate request" to ensure more people followed the rules.
He said it was "unfair" for all the legal enforcement responsibility to fall on the police.
The BBC has asked three major supermarket chains to comment.
A spokesman for Tesco said it would continue to follow government guidelines, which urge supermarkets to encourage mask wearing as much as possible.
Mr Burnham said: "I'm not asking staff or checkout workers to be doing this. I'm asking supermarkets to have security staff to it, because most of them do employ security staff.
"Let's remember, all of the supermarkets have made a lot of money throughout this whole situation. I don't think it is too much to ask.
"If they say they can't afford to do it everywhere, I'm saying they should be doing it in Greater Manchester with the situation we face, and other areas that are facing greater restrictions."
'Job of the police'
A spokesman for the British Retail Association said the legal responsibility to enforce mask wearing should continue to reside with the police.
"It's the job of the police and not the supermarkets. That was very clear in the government guidelines," he said.
Mr Burnham also called on the government not to bring in "knee-jerk measures" as coronavirus cases continue to rise in some parts of Greater Manchester.
He said he did not want to see a full lockdown in Oldham, where the rate of infections is currently the highest in the country.
But he said that he and council leader Sir Richard Leese had written to Health Secretary Matt Hancock to ask that there was no further easing of restrictions in the city region this weekend.
Extra restrictions on socialising between households were introduced in Greater Manchester, as well as parts of Lancashire and Yorkshire, at the end of July following a spike in cases.