Deputy prime minister Dominic Raab has urged Conservative rebels to back the government’s plan B restrictions, arguing that Covid certification is not a “big step or a slippery slope”.

Boris Johnson is facing the biggest Commons revolt of his premiership on Tuesday as MPs prepare to vote on Covid passes for large venues, the extension of mandatory face masks and changes to self-isolation rules.

At least 70 Tories are expected to rebel and vote against the government later today, with backbencher Marcus Fysh comparing the health pass for nightclubs and large events to Nazi Germany.

But the deputy PM claimed that Tory backbenchers’ concerns over the mandatory introduction of passes are “overstated”.

Mr Raab told Sky News: “Even if you haven’t had the double jab or, in due course, the booster, you can still rely on the lateral flow test – which is why I think some of these concerns about this are overstated.”

Arguing it is not just proof of vaccination but of a negative lateral flow test as well, he told Times Radio: “I don’t think this is a big step or a slippery slope, but I do understand the concerns and that’s why we should have a proper debate.

The deputy PM added: “Ultimately, I think people should vote for these measures – they are a proportionate, targeted approach given what we don’t know and the precautionary approach we need to take, just temporarily, while we get to grips with omicron.”

Asked about Mr Fysh’s remarks comparing certification to Nazi Germany, Mr Raab said: “I don’t accept it and I don’t think it’s right and I don’t think it’s a reasonable critique. But I do understand concerns that people have.”

He added: “I don’t think that is particularly intrusive thing to do in order that we protect ourselves and others around us … it’s a sensible, precautionary public health measure that will protect us all.”

According to a tally of Tory MPs by The Spectator magazine, 79 Conservative MPs – including former ministers, some of the 2019 intake, as well as lockdown-sceptics – have said they will vote against or abstain on the plan B measures.

It is reported that up to 10 ministerial aides could resign to oppose the controls, with up to four votes on the measures expected to take place on Tuesday evening. But the measures are expected to pass the Commons with the support of Labour, who back tighter controls.

Mr Raab did not rule out further Covid restrictions being considered for Christmas or New Year, saying: “These issues are always discussed but we have got plan B – that’s what we think is required over the Christmas period.”

The justice secretary also acknowledged “teething problems” after people were seen queuing for hours to get coronavirus booster vaccines and the booking website struggled to cope with the demand for appointments.

Meanwhile, Tory MP Sir Roger Gale told Times Radio on Monday evening he had considered submitting a letter of no confidence in the prime minister and warned if the voters send a message to No 10 at Thursday’s by-election in North Shropshire “then that could be a tipping point”.