"Bruising," they always say about the kind of week that's happened to Iain Duncan Smith. As I write, it's only Tuesday. You'd have to ask, without wishing the minister ill, at what point a bruise turns into an internal haemorrhage.

He started on the Today programme on Monday, maintaining that the problems with universal credit were mere trifles, because look at the shambles that was the working family tax credit. I remember that, but only just – it was a decade ago. Some of the payments were delayed, and a lot of overpayment was clawed back. If I were IDS, I wouldn't mention it. Not because it looks pathetic, trying to wriggle out of your own catastrophe by pointing to something that happened to someone else 10 years since. But because it recalls a time when this was the worst the Department for Work and Pensions would do to you: delay, overpayment and recovery.

All these things caused hardship and anxiety. Compare them, though, to deliberately withholding benefits on the basis of specious sanctions; mass-scale food-bank usage, as hardship tips into desperation; and a regime in the DWP that is as unlikely to overpay in a rush of generosity to the head as it is to accept opportunity and dignity as government objectives. This comparison serves Duncan Smith ill. It is a curiosity of the opposition that not only is it silent on matters of policy, but it even waits for a minister to point out that New Labour's cock-ups were kinder than his, and felt a lot less painful on the ground. Bring back Dawn Primarolo. (There's a sentence I never thought I'd write.)

Anyway, haste him, 2013's very own Ebenezer, to the work and pensions committee that Monday afternoon, where they wanted to know a little more about this shambles, and more still about his persistent failures of truthfulness. Not so, he insisted. He had only been reprimanded twice by the UK Statistics Authority – which, when you consider how much he says, is brilliant.

He has a point here. As a leader column in the Economist famously pointed out: "Questionable numbers have floated out of [his] office into the public debate like raw sewage." Only that morning, he had claimed that Labour's tax credit errors cost "£30bn in fraud". Nobody knows how he reached this figure. Even if he rolled overpayment together with every other DWP error, together with claimant error, together with claimant fraud, it still wouldn't add up: not unless you then added in all other benefit error (plus fraud), and calculated it over 10 years. Realistically, how can you expect a statistics authority to keep up with a person like this?

The problem is – as Glenda Jackson demonstrated quite well at the end of the committee hearing in her audible exasperation – he reduces debate to the level of disbelieving outrage, rounding on his opponent with a patrician fury of his own. (My personal favourite was the time he turned on Owen Jones on BBC1's Question Time and said: "We've heard quite a lot from you." A nation waited, in vain, for the concluding "pleb" or "worm" that would have ended, or at least interrupted, his career. Next time, oppos. There's always a next time.)

Whenever you think you've got him, that's exactly the point at which he's slipped away – because, the thing is, he doesn't care about accuracy. He doesn't care about being reprimanded; his own reputation for truthfulness is a price he is prepared to pay, to get this untreated sewage floating around the debate. (In truth, he took that hit some time ago.)

He doesn't care that the money frittered away by this reckless, apparently unstewarded project is more than it will ever save; that IT costs met with a shrug today will reverberate into most unjust parsimony tomorrow.

He doesn't care about the internal logic of his position, that a man so in thrall to the benefits of wedlock has created a system in which large families will have no choice but to separate into two households. He doesn't care about the shonky foundations of the welfare cap – that for want of an open debate about statutory rights, it is really just a cap on housing benefit, leaving people to scratch together the shortfall with their other benefits.

None of this bothers him in the slightest; indeed, it actively pleases him to hear it brought up, because the slur to his putative honour will justify the bluster he vents to obscure his real purpose. He wants people to stop being able to rely on social security.

From his perspective, the route is irrelevant; we could get there by a reasoned political process, whereby we agree – or at least our representatives do – that we no longer want a security net, that we no longer consider it our common purpose to look out for each other.

Or, failing that, we could simply make the system so incompetent and faceless that charities have to step in.

Or he could spread so much misinformation that we all lose faith in a government's ability to plan or distribute.

Or he could demonise recipients so much that mainstream debate no longer felt able to distinguish between a fraudster and a claimant.

What he's doing is pursuing all of the above, pell mell, in any order, and hoping for the best. Facts will never silence this tragically mis-named Quiet Man of Politics. We need to call his grand project what it is: not an accidental shambles but deliberate vandalism.

Twitter:@zoesqwilliams