Employers may be able to draw up contracts requiring new staff to get a coronavirus jab, Justice Secretary Robert Buckland has suggested.
The cabinet minister said it was unlikely bosses could legally require workers to receive a jab under existing agreements, but indicated it could be tested in court.
Pimlico Plumbers and Barchester Healthcare, one of the UK's largest care home groups, are among those who said they will not take on new staff who refuse to have the COVID-19 injection on non-medical grounds.
Downing Street has said it would be "discriminatory" to force someone to have a coronavirus vaccine in order to keep their job.
But Mr Buckland told ITV's Peston: "I think it would depend very much on the terms of employment and the particular contract.
"Generally speaking I'd be surprised if there were contracts of employment existing now that did make that approach lawful. I think frankly the issue would have to be tested.
"I can see that in particular work environments the desirability of having a vaccine is going to be higher than in others."
Asked if it is up to employers to test the system if they do not want people who decline vaccines working for them, Mr Buckland said: "I think that has to be the case because we're dealing with existing terms of contracts of employment, thousands of existing contracts."
Pimlico Plumbers founder Charlie Mullins said lawyers had approved of his approach for new employees.
"More and more businesses are saying the same things," he told Channel 4 News.
"We've already had the contracts drawn up, lawyers are very happy with them. They say it's legal under health and safety laws and we have an obligation to protect our staff and our customers."
Barchester Healthcare, which runs more than 200 care homes, said last month it will adopt the new policy because of the vulnerability of its residents.
The prime minister's official spokesman has said: "Taking a vaccine is not mandatory and it would be discriminatory to force somebody to take one."