Fierce criticism of ministers is a normal feature of democratic politics. Such attacks can have a theatrical aspect. But it is important that substantive attacks are not dismissed as point scoring, because it matters that powerful individuals are held to account for mistakes. The £33m settlement reached by the government with Eurotunnel last week, following the disastrous awarding of contracts for new ferry routes as part of Brexit planning, is the latest in a catalogue of errors made by transport secretary Chris Grayling – the total cost of which Labour estimates at £2.7bn. It must also be the last. As long as he remains in the cabinet, the joke about Mr Grayling is on taxpayers. If he doesn’t resign, he should be sacked.

Not all policy failures are the same, and judgments are made on the basis of ideology as well as competence. Mr Grayling has shown himself to be illiberal even by Conservative standards. In 2010 he argued that bed and breakfast owners had the right to bar gay and lesbian guests. As justice secretary, he banned prisoners from receiving books from relatives. A committed Brexiter, he also had a hand in one of David Cameron’s worst decisions – as leader of the House of Commons, he helped force Mr Cameron to allow his ministers to campaign to leave the EU.

But it is Mr Grayling’s incompetence that makes him unfit for the high public office he now holds. His ministerial career began at the Department for Work and Pensions, meaning that he has a share of responsibility for the still-unfolding fiasco of universal credit. But as justice secretary he was fully in control of the failed part-privatision of the probation service. This is a national scandal, described in the latest report from the National Audit Office as “extremely costly”. In addition to the £171m bill for cutting short the contracts, the number of people on short sentences recalled to prison has skyrocketed. More recently, as transport secretary, Mr Grayling oversaw the chaos unleashed last summer when altered rail timetables left passengers stranded. His defence was that it was hard to overrule industry bosses.

It has become a truism that public faith in the UK’s political institutions is being tested. Like the rest of political debate at the moment, this discussion is monopolised by Brexit. So politicians and commentators warn of the anger and alienation that could be unleased by another referendum, or by the perception that politicians are reneging by some other means on their side of the Brexit deal. And it’s true that there are real risks, whatever happens next.

But there are other dangers than a Brexit delay. The suspension of ordinary accountability mechanisms, which would in more normal times have seen Mr Grayling moved out of a job he has failed to do well, also corrodes voters’ confidence in their elected representatives. The vast majority of ministerial resignations from Mrs May’s government have been walkouts due to Brexit, with Amber Rudd and Tracey Crouch the exceptions. Even after misleading parliament over universal credit last year, Esther McVey was allowed to quit at a time of her own choosing, on a point of ideology.

It’s good to see policies change in response to outsourcing failures. The probation experiment is over; NHS bosses are making the case against competition in the health service. But if ministers aren’t held to account for such wasteful exercises, people will feel justified in their cynicism. Politicians should instead be doing everything they can to counter this. Failing Grayling is not funny anymore.