Leaders from Britain's hospitality industry and a group of Conservative politicians have roundly rejected a proposal from Prime Minister Boris Johnson that pubs could turn away customers who cannot prove they have been vaccinated, saying it was "unworkable".

The prime minister made his proposal to a liaison committee of senior members of Parliament that is reviewing the idea of whether people should have to show vaccine passports or negative tests as lockdown measures ease.

Johnson made the comments ahead of Thursday's Parliament vote that extended some parts of emergency COVID-19 legislation, known as the Coronavirus Act, to the end of September.

The act, which was passed a year ago as the country went into lockdown, includes temporary powers that allow authorities to bar protests, shut down businesses and restrict travel.

Backbench MPs have denounced the act as "the most draconian detention powers in modern British legal history", though the extension vote still passed with support of the opposition Labour Party.

One vocal critic is MP Steve Baker, who was quoted by the Daily Telegraph as saying that the plans for vaccine passports could lead to a "two-tier Britain that prevents pregnant women from taking part in society".

"First, they said we'll need them to watch the football, and today that it may be papers for the pub," he added.

It was a "ghastly trap that we must not fall into", he said.

When asked at Wednesday's committee hearing about the possibility of a vaccine passport program for pubs, Johnson said: "I think that's the kind of thing that may be up to individual publicans. It may be up to the landlord. The basic concept of vaccine certification should not be totally alien to us."

Kate Nicholls, chief executive of UK Hospitality, said the idea would be "unworkable".

"It's crucial that visiting the pub and other parts of hospitality should not be subject to mandatory vaccination certification," she said in a social media post.

"It is simply unworkable, would cause conflict between staff and customers and almost certainly result in breaches of equality rules."

The chief executive of a major pub chain warned the concept could lead to issues around "discrimination" and "data protection".

Speaking to the BBC's Today program, Jonathan Neame, chief of Shepherd Neame, said he would not make vaccine certification a mandatory condition for people to visit his pubs.

"The whole essence of a pub is that they are diverse and inclusive environments, where everybody, and families in particular, are extremely welcome," he said.

"It's absolutely fine to exclude people where there is a situation of bad behavior or drunkenness, and that's already enshrined in law, but if you're going to exclude people for what they are, or what they have not done, that's a wholly different issue which does touch on discrimination, civil liberties, and in this case data protection issues."