A cabinet minister has defended Boris Johnson and Rishi Sunak over their Partygate penalties, equating them to fines issued to speeding motorists, as the prime minister prepares to argue he did not mislead parliament. When asked if lawmakers could be lawbreakers, the Northern Ireland secretary, Brandon Lewis, told Sky News on Tuesday morning: “I think we do see consistently, whether it is through parking fines or speeding fines, ministers of both parties over the years have been in that position. “We’ve had prime ministers in the past who have received penalty notices, from what I can see, and also frontbench ministers. “I saw there was a parking notice that Tony Blair had once. We’ve seen frontbench Labour ministers [be fined] and, let’s be frank, government ministers as well.” He added: “You’ve asked me, can someone who sets the laws and the rules, can they also be someone who breaks the rules? That clearly has happened with a number of ministers over the years.” Later on BBC Radio 4, Lewis clarified that he was not trying to equate a speeding ticket with the “sacrifices people made through Covid”, but added: “A minister or a parliamentarian getting a fixed-penalty notice, accepting that, acknowledging that, and apologising for that, is the right way to handle it.” Facing claims that the prime minister deliberately misled MPs over his knowledge of a Downing Street party, Lewis said Johnson’s apology did not mean that what he had earlier told parliament was not correct. On Sky News earlier, asked when Johnson came to the view he’d broken the law, Lewis said it was “when the police had issued a fine”. Johnson is expected to use this defence as he faces MPs for the first time since he received a fixed-penalty notice for breaking his own Covid laws by attending a No 10 lockdown party for his birthday. He is expected to make a “full-throated apology” in the Commons on Tuesday, according to PA News agency. However, Johnson, thought to be the first sitting prime minister to be criminally sanctioned, is expected to stop short of addressing the Partygate allegations. He will call for a renewed focus on the Ukraine crisis, and the government’s controversial policy to send asylum seekers to Rwanda. Downing Street later refused several times to back Lewis’s comparison of the Partygate fines to fixed penalty notices issued to motorists for speeding. Boris Johnson’s spokesperson said he had “talked about understanding the strength of feeling about this issue, which is why he has apologised and fully respects the outcome of the police investigation”. He did not dispute briefings over the weekend saying the prime minister thought he had done nothing wrong, but said Johnson had made clear that “many will feel that he fell short” of the rules. After the Conservative MP Michael Fabricant accused many teachers and hospital workers of having after-work drinks, too, Johnson’s spokesperson could not point to any evidence of that happening. “I can’t speak to what may or may not have happened in in other workplaces where people are required to be in work,” he added. If Johnson is fined again by police, No 10 confirmed he would say so publicly. Lewis talked down any prospect of a leadership challenge against Johnson, saying the prime minister was focused on “how we move our country forward” and getting the “big calls right” – pointing to Brexit, Covid, the war in Ukraine and the cost of living crisis. While Johnson hopes to ride out the storm, the full Whitehall report into Partygate by Sue Gray is yet to be published, and police are still investigating up to six further gatherings where Johnson is said to have been present. In the Commons, opposition MPs will question why the prime minister insisted repeatedly that no rules had been broken. Emily Thornberry, the shadow attorney general, told BBC Radio 4’s Today programme: “We’re not going to get the result we should get unless the prime minister looks into his own conscience and decides he should do the right thing.” She added: “We’re not going to get that because the PM doesn’t tell the truth.” While Thornberry said Johnson would get “a good reception” for his actions on the Ukraine crisis, she said he was expected not only to give “another weak apology” but accept he lied to parliament and explain how he “squares that” with his own ministerial code. Opposition parties are pushing for the Speaker, Lindsay Hoyle, to allow a vote on a debate about whether the prime minister should be held in contempt of parliament, potentially launching an investigation into whether the Commons was misled. Anything that requires a vote, however, is likely to fail given the Tories’ large majority. On Saturday, Conservative MPs across the country said they believed traditional supporters were abandoning them after the prime minister’s penalty. The former immigration minister Caroline Nokes wrote in the Observer that she was sticking with her decision to submit a letter of no confidence in Johnson.