Men lie for many reasons: to boost their ego, to hide their failings and to advance their ambitions. The sole impressive characteristic of Iain Duncan Smith – the winch that lifts him out of his otherwise incurable mediocrity – is his ability to lie for every reason imaginable, even when he knows his audience must find him out. If he told me that two plus two made four, I'd ask for a second opinion.

Last week, the work and pensions secretary announced on his department's website that he was "very pleased that the supreme court unanimously upheld" his programme to force the unemployed to work without pay or lose their benefits. "Ultimately, this judgment confirms that it is right that we expect people to take getting into work seriously."

If the judges had Duncan Smith before them, they could accuse him of the old misdemeanour of suppressio veri: the suppression of a truth he was duty bound to disclose. Nowhere in the government's propaganda did Duncan Smith admit that the supreme court had, in fact, found against him on every ground of appeal he had raised. Even though he had protected his department's hard line on the young by rushing through retrospective legislation, the supreme court still hammered him. The government had not provided "sufficient detailed prescribed description" of the work placement schemes on offer, the judges said. The unemployed could not make an informed decision on how best to find work. Their ruling will help young people Duncan Smith's department had pushed into quack schemes on pain of losing their benefit. As Public Interest Lawyers, the rather inspiring firm of solicitors that took on the test case said: "You should not believe the DWP when it says that the judgment makes no difference. Jobseekers who have not been provided with adequate information can now seek the repayment of their benefits."

Without a shred of hope of receiving a coherent answer, I asked a flak-catcher in the Department for Work and Pensions press office to explain his master's behaviour. Why had Duncan Smith just said that the supreme court had ruled that he was not guilty of pushing the young into "forced labour", but failed to add that it had condemned him on every other point? The wretched man blocked, stammered, dodged and weaved. I almost felt sorry for him. There must be better ways of making a living, even in these hard times.

If you think that such deceits are the normal stuff of politics, consider the story's sequel. As Duncan Smith realised he was losing the case, he went on the BBC to denounce Cait Reilly, one of the claimants who was challenging him in court. Despite receiving benefits, the 24-year old had refused to work for nothing in Poundland, he claimed. She was part of "a group of people out there who think they are too good for this kind of stuff". A "job snob", in other words; a scrounger, who was not prepared to get off her backside and put in the hours necessary to secure remunerative employment.

If he had checked his facts, a task that seems beyond him, Duncan Smith would have discovered that Ms Reilly had been a volunteer at a Birmingham museum. She worked there gratis because she hoped one day to be taken on by a museum or gallery. Reilly objected to Duncan Smith's minions taking her out of the museum and sending her to Poundland instead because they were stopping her fulfilling her ambition for no reason at all.

Maybe I am over-sensitive, but I find the spectacle of a powerful old man falsely condemning an honourable young woman distasteful in the extreme. Duncan Smith threw out any allegation that came into his head just to do her down. On second thoughts, that is more than distasteful – it is disgraceful.

As I have mentioned before , Duncan Smith has form. He claimed that around a million people have been stuck on a working-age benefit for at least three out of the past four years, despite being judged capable of preparing or looking for work. His claim was false. He claimed that his benefit cap had encouraged 8,000 people to find work. Not true either as the UK Statistics Authority pointed out in a stinging reprimand .

Why doesn't he give us a break? The short answer is that his department is falling apart and he has to spin and bluster to cover the shambles he has presided over. His once-grand plans for a universal credit to cover the whole country have shrunk to a pitiful pilot project. Hailed by Duncan Smith and rightwing London as the incentive that would propel the unemployed into work, universal credit has become Whitehall's equivalent of a layabout yob: nothing can make it work. His equally overhyped "reform" of disability welfare payments looks as if it is going the same way.

There is a danger here of seeing Duncan Smith's failures as examples of Tory dishonesty and bureaucratic incompetence. But we should not lose sight of the human suffering that accompanies them: the thousands driven to food banks because Duncan Smith's department cannot pay their benefits; the cheapskate firms that, with Duncan Smith's connivance, tell the chronically ill that they are fit for work when they are no such thing.

In Matthew D'Ancona's history of the coalition, George Osborne says: "You see Iain giving presentations and realise he's just not clever enough." He most certainly is not. Yet there is no pressure from the British right to remove him from office. On the contrary, Tories acclaim Duncan Smith and Michael Gove as the coalition's two heroes. As well as bellowing to hide his all-too evident weaknesses, Duncan Smith spins to encourage his supporters, who, incredibly, still admire him and praise him as a great reformer.

That he still wins such praise tells us much about the British right. It cannot believe any more that Duncan Smith is ending welfare dependency. It can no longer pretend that his tough love is helping the unemployed into work. His great schemes are in ruins. His reputation for probity is in tatters.

Conservatives continue to admire Iain Duncan Smith, nevertheless, for one reason and one reason only: he is cutting the money going to the poor, the sick, the handicapped and the young. That's it. That's all there is to him now. And the right loves him for it.