Video report by ITV News Political Correspondent Carl Dinnen
Boris Johnson is facing the real prospect of a successful rebellion by backbench Tories over proposals to use "coronavirus certificates" as a way to reopen the economy.
The potential use of certificates - which would include vaccination status, test results or evidence of someone having contracted and recovered from Covid-19 - is opposed by at least 40 Conservative MPs and Labour is also sceptical about the measure.
The government is currently reviewing the idea will put proposals to a vote in Parliament if successful - where it could be possible for Tory rebels and opposition MPs to inflict a rare defeat.
One side of the debate is opposing the measure vociferously, saying certificates would be discriminatory to those who do not want to be vaccinated, while the other is lauding them as a way to reopen venues such as theatres and nightclubs.
ITV News Political Correspondent Carl Dinnen explains the opposition to vaccine passports:
Tory MP Steve Baker, deputy leader of the Covid Recovery Group, labelled the proposals "entirely un-British" as he demanded Health Secretary Matt Hancock explain in the House of Commons why Covid certification would be necessary.
In a stinging statement he said: "The last thing we should do is allow Covid to have the victory of changing our country forever into the miserable dystopia of Checkpoint Britain."
Since the idea was first floated the government has treated it with caution, with the prime minister previously acknowledging the “moral complexities” around bringing in a domestic vaccine passport scheme.
But at Monday evening's press conference he did not rule out a policy requiring coronavirus certificates for entry to large events.
He said the idea of someone having to prove they're not spreading a disease "can be a sensible one" but added the government is "some way off finalising any plans for Covid certification in the UK".
On Tuesday he confirmed ministers are "going to look at the role of a number of signals that you can give that you are not contagious", such as immunity as a result of having had Covid-19, vaccination status and testing as factors.
Vaccine passports to facilitate international travel are very likely to be required in the future, the PM said, as other countries seek to ensure tourists do not bring disease with them.
Vaccines minister Nadhim Zahawi on coronavirus certification:
Mr Johnson confirmed certificates would not be used in the next two steps out of lockdown, on April 12 and May 17, but a government document published on Monday suggested they will eventually be in use.
"Even without government intervention, Covid-status certification is likely to become a feature of our lives until the threat from the pandemic recedes," the document said.
The vaccines minister said if a review into certificates, currently being carried out by Chancellor of the Duchy of Lancaster Michael Gove, finds they could be useful, then the government will put the idea to a vote in Parliament.
Video report by ITV News Political Reporter Shehab Khan
If it gets that far, the government would face the serious prospect of a rare defeat in the House of Commons.
A cross-party coalition of more than 70 MPs - including up to 41 Tories - has agreed they would oppose domestic vaccine passports if put to a vote.
Senior Tories such as David Davis have indicated they would vote against the plan, along with Liberal Democrats leader Ed Davey, former Labour leader Jeremy Corbyn and it also looks like the current leadership will be called for its MPs to reject any motion.
Senior Tory Mark Harper, chairman of the lockdown-sceptic Covid Recovery Group, warned Covid status certification "will lead to a two-tier Britain".
Sir Keir Starmer said it would be against the "British instinct" to use certification and shadow health secretary Jonathan Ashworth told BBC Breakfast that Labour was "very sceptical" about the idea.
Interim findings of the government's review said public transport and essential shops would not require vaccine passports.
But Mr Ashworth said: "I'm not going to support a policy that, here in my Leicester constituency, if someone wants to go into Next or H&M, they have to produce a vaccination certificate on their phone, on an app.
"I think that's discriminatory."
He said while it "makes sense" to ask people to take a test before going to events such as football games "we don't think asking you to produce a vaccination passport, which is this digital ID card, is fair".
"It's discriminatory," he said.
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