British companies are looking to draw up “no jab, no job” contracts for employees, as the government admitted that it was “up to businesses” if they wanted workers or customers to hold coronavirus vaccination passports.

Law firms said some companies, ranging from UK care-home operators to large multinational groups, were considering employment contracts requiring new and existing staff to have vaccinations once Britain’s adult population has been offered jabs.

Boris Johnson, prime minister, has said the government will not introduce domestic vaccine passports — an idea that raises many moral and legal issues — but on Tuesday Nadhim Zahawi, vaccines minister, acknowledged that some companies might press ahead with their own schemes.

“It’s up to businesses what they do, but we don’t yet have the evidence of the effect of vaccines on transmission,” Zahawi told the BBC. He had previously warned that the use of domestic vaccine passports would be “wrong”.

Ministers are deeply uneasy because they fear that such passports could lead to discrimination against people who cannot, or will not, receive a Covid-19 jab. They want to avoid any impression that people are being coerced into getting a vaccine.

The government is not planning to outlaw the use of domestic vaccine passports by companies, but officials expect the use of such documents to be tested in the courts.

“Companies must ensure their business practices are legal and don’t discriminate against customers or employees,” said one government official.

Barchester Healthcare, which runs more than 200 care homes, has said it will not hire new staff who refuse the Covid-19 vaccine on non-medical grounds. Pimlico Plumbers has also announced a “no jab, no job” policy for new recruits.

Law firms, which declined to be named, said some companies were also looking at requiring existing employees to have coronavirus jabs.

Most employers are wary of any mandatory requirement for staff to be vaccinated, which would mean handling sensitive medical data, and could leave them open to legal challenges on discrimination grounds if workers refused jabs because of a religious belief, pregnancy, or a health condition that could constitute a disability.

The CBI business group said there was no case for compulsion, adding that businesses were “committed to doing everything they could to inform and engage their employees on the benefits of the vaccine”. The CBI said that rapid, mass Covid-19 testing was the key to making workplaces safer.

“The UK government hasn’t made the vaccine compulsory, so neither can employers,” said Peter Cheese, chief executive of the CIPD organisation for HR professionals. “Nor should they be restricting people coming into work based on whether they have had the vaccine.”

The CIPD said members in various sectors including care, dentistry and food manufacturing were asking how to handle situations where staff refused vaccinations.

One City of London lawyer said the introduction of clauses in employment contracts requiring workers to have vaccinations would be risky, because of the possibility of discrimination claims, but were more likely to be defensible in sectors such as care because of the prevalence of vulnerable patients.

Another City lawyer said some multinational groups, including one large energy company, were considering such clauses.

James Davies, partner at law firm Lewis Silkin, said any company seeking to amend workers’ current contracts would have to first gain consent — a step not necessary for new hires.

The UK events industry has been quickest to grasp the potential for vaccine passports or rapid testing as a way to restart mass gatherings.

“As an industry we will consider any route that gets our doors open again safely and are focused on working with the government to make that possible after nearly a year of closure,” said Greg Parmley, chief executive of Live, the live music sector trade body.

The wedding sector has offered itself up as a guinea pig for trialling vaccine passports as a means of allowing events to take place.

But others in the hospitality industry are critical of the idea, including trade body UKHospitality.

Several companies working on vaccine passports for international travel said their technologies were suitable for UK employers.

In January, biometrics company iProov and cyber security group Mvine began trialling their Covid-19 passport, with a £75,000 investment from Innovate UK, a government agency that funds business and research collaborations.