In a world of fake news and downright mendacity, lying to parliament may seem like just another day in politics. But the work and pensions secretary Esther McVey’s non-apology in the Commons on Wednesday, deliberately repeating fabrications about the universal credit (UC) disaster, takes indifference to facts to a new level of insolence.

The comptroller and auditor general, Sir Amyas Morse, who is in charge of the rigorously independent National Audit Office, has a reputation for strict propriety and extreme circumspection in his public comments. It takes unprecedented misrepresentation of an NAO report to force him to take the extraordinary step of publishing his letter of reprimand to the minister in charge of the Department for Work and Pensions. What else can he do when this minister has the effrontery to refuse to meet him? She plainly takes a Trumpist approach to inconvenient realities, so why bother meeting this annoying nitpicker?

It’s no surprise that a minister who misleads parliament and thumbs her nose at the NAO is even more indifferent to the people who really matter – the millions suffering her department’s infliction of extreme hardship as they are transferred to UC. Here’s the core of the matter: last month the NAO delivered one of its most damning reports on the design, delivery and future prospects of this new system, which brings together six benefits, saying it was flawed from the start when its progenitor, Iain Duncan Smith ignoring all warnings and made extravagant claims for how new “conditionality” would propel idlers into work. He wasted a fortune on failed IT and plunged people into deeper poverty, debt and rent arrears. The NAO found that the DWP’s own surveys showed 40% of claimants said they were experiencing financial difficulties, 20% were not paid in full on time, and 25% said they couldn’t make an online claim. The NAO concluded: “The benefits that it set out to achieve through universal credit, such as increased employment and lower administration costs, are unlikely to be achieved.” Worse, it found a quarter of new claims were paid late, so debts and rent arrears soared: when universal credit is rolled out, local food banks see a 30% upsurge in use, according to the Trussell Trust. Because payment takes five weeks, 60% of new claimants need an advance, which becomes a debt: the NAO says the system will never deliver all claims on time.

That’s the human hardship. But the DWP’s maladministration has wasted £2bn: after eight years UC is still only rolled out to 10% of claimants. The cost, says the NAO, is an eye-watering £699 per case, against a target of just £173. Benefit cuts, including those imposed on those transferring to UC, are due to put a record 37% of children into poverty by 2022, warns the Institute for Fiscal Studies. McVey is the fifth DWP secretary since 2010: she took on the job after Justine Greening wisely preferred to quit the cabinet rather than defend the irreparable damage done by Duncan Smith. The NAO report concludes bleakly that in so deep, there is “little realistic alternative but to continue with the programme”. McVey has already proved herself an eager axe-wielder: as minister for disabilities in 2013 she was slippery with facts and callous to claimants. Morse was fired up by her claim that his report called for UC to be rolled out faster: on the contrary, he points out in his letter, his report said, “the department must now ensure it is ready before it starts to transfer people over from previous benefits. This will avoid the department’s performance declining further as it faces higher claimant volumes. I also recommended the [DWP] learns from experiences of claimants and third parties, as well as the insights it has gained from the rollout so far.”

Even more impudent was her claim that his report was based on outdated statistics: he spells out how carefully figures were squared with DWP officials right up to publication. All this matters critically to millions of low-paid families on the brutal sharp end of UC.

Cavalier trashing of the NAO, our sacred keeper of the flame of facts, evidence and honest auditing, is profoundly alarming. This government, engaged in monumentally perilous Brexit negotiations, needs now more than ever to engage with difficult truths without flinching from inconvenient realities.

But instead McVeyism is everywhere. Duncan Smith, the architect of UC and many other calamities in one of the most disaster-causing political careers of our time, had the gall to tell parliament that Morse’s report is “a shoddy piece of work”. As he appears on our screens day after day propounding preposterous Brexit unrealities, broadcasters should ask if there comes a point when a politician found responsible for an act of such monumental failure is stripped of all public credibility? As for McVey, her deliberate misleading of parliament is considerably worse than the actions that led to Amber Rudd’s resignation as home secretary earlier this year after she inadvertently misled the home affairs select committee. But there is no sign of any such honourable resignation from McVey.

• Polly Toynbee is a Guardian columnist