Described as “misleading spin” that would never be enforced, by shadow attorney general Lord Falconer, the move was confirmed yesterday by Boris Johnson’s spokesman.

The sentence is the maximum permitted under the Forgery and Counterfeiting Act 1981.

Lord Falconer said, however, that the policy was being used as a distraction.

“It is misleading spin. No judge is ever going to sentence anyone to anything like 10 years for lying on a passenger locator form. If someone was forging and selling fake vaccine certificates that might be a different matter, but that is not what the secretary of state is referring to.”

He added: “The far more likely scenario is a judge sentencing you to prison for a month or so. It will be nothing like 10 years. It will play no part in the actual policy. All it does is distract from the fact that they have taken so long to come up with this proposal.”

Sir Charles Walker, vice-chair of the 1922 Committee of Conservative backbenchers, said the proposal was “utterly ridiculous”.

Sir Charles told Sky News: “Are you really seriously suggesting, secretary of state, that we’ve got enough prison capacity to start locking up 19-year-old silly kids for 10 years? What a stupid thing to say. It demeans his office and his position around the cabinet table.”

Former attorney general Dominic Grieve QC said the number had been “plucked out of the air” and that such a sentence could only be imposed for forgery.

“But this is a regulatory offence, and no regulatory offence I can think of, of this type, attracts a 10-year maximum sentence,” he told the BBC.

Former chief prosecutor for north-west England, Nazir Afzal, said: “You will get a longer sentence for lying about your travel than you do for carrying a firearm in the street. This wrongly assumes that the police have the resources to investigate your travel arrangements and that the courts with their two-year backlog of trials can hear your case.

“Of course, people with the means or connections can get round this easily as we have seen many times.”

Stuart Nolan, chair of the Law Society of England and Wales’ Criminal Law Committee, said: “This is contentious; ministers are talking about trampling peoples’ liberty and it is not being debated. And it is rightly contentious given the maximum sentence for theft is now seven years and there’s a high bar for that.

“There is also the practical question of how they are going to enforce it. Boris Johnson wants 10,000 more prison places; there’s a campaign to get more police officers; there have been 10-plus years of underinvestment in the judicial system; an extraordinary backlog going back to pre-Covid times and this could be a mammoth task if people fail to comply with quarantine.”