They walk on air, for now. This government can say and do whatever it damn well pleases, with Labour awol until it has a leader. And George Osborne has just pulled off an outrageous betrayal of the cohorts of over-65s who gave the Tories their victory, yet nothing has happened.

Barely 10 weeks since a manifesto pledge to cap the care costs of elderly homeowners, Osborne has abandoned it. This perfidious U-turn is every bit as shocking as was the Liberal Democrats reneging on tuition fees. That’s just one example of the Conservatives’ current air-walking untouchability. But their majority is only 12, they make bad errors, and no one can fool everyone all the time with factoids and fictions.

Osborne, writing in the Guardian yesterday, used his sharpest political stiletto on Labour. Hasta la vista! Suck it up, losers! The voters have spoken, so vote for these benefit cuts or stay in the wilderness because “three in four people – and a majority of Labour voters – think that Britain spends too much on welfare”.

He and his echo chambers have for too long promulgated welfare myths and untruths, with polls showing people wildly overestimate benefit rates. His £20,000 benefit cap is deadly cunning, implying that their income is not the fault of unavoidably high rents. Large families are few and falling in number, but one good anecdote about a dysfunctional feckless household distracts from the savage effect of cuts to the rest of the working poor.

For slippery tricks, look closely at what Osborne wrote: “In 1980 working-age welfare accounted for 8% of all public spending, but by 2010 it had risen to nearly 13%. While this country has just 1% of the world’s population and produces 4% of its wealth, it accounts for 7% of global welfare spending. That’s not sustainable.” Think carefully – these are non-sequiturs, the first misleading, the second nonsensical.

Jonathan Portes, the head of the National Institute of Economic and Social Research, points to figures from the Office for Budget Responsibility showing spending on working-age welfare didn’t surge under Labour, but rather under Thatcher and Major. Was it “unsustainable” then? It stayed pretty flat under Blair/Brown: unemployment fell, but Labour brought in tax credits to redistribute towards low earners.

Those credits were an admirable policy to hold incomes steady against the rising forces of inequality. Watch out too for that word “unsustainable”. It’s Tory-speak for anything they don’t want to sustain: listen how often they use it about NHS funds. John Whittingdale says it about the BBC licence fee.

Their perfidious U-turn on care costs is every bit as shocking as was the Liberal Democrats reneging on tuition fees

Now examine Osborne’s claim that Britain has “7% of global welfare spending”. He averages all the world’s nations, down to the poorest, to compare with Britain: yes, we spend more than countries with no social security, but considerably less than, say, Germany and France. Only 3% goes to the unemployed, while half goes on rising pensions. Sustainable? That’s a matter of political choice, so Osborne calls it “an unaffordable welfare state”.

Now let’s look at his “national living wage” of £9 by 2020, that clever budget coup – though that’s far below the real living wage in five years’ time. In the article he claimed: “That will mean a pay rise of over £5,000 a year in cash terms for 2.7 million currently on the minimum wage.” Not so, says Portes.

The chancellor has cheated. Only 0.75 million people are on the current minimum wage, but he has lumped in another 2 million earning somewhere below his £9 who stand to gain something. He excludes under-25s, who won’t gain. Many will be in jobs offering far fewer than the 40 hours a week he presupposes. So, says Portes, the “average cash gain will be far less”. But politically Osborne’s factoids fly – so his slippery numbers sound as if the pay rise compensates for the impoverishing £12bn of benefit cuts.

What makes Osborne so plausible is that of course he is right that it’s good for dignity and for taxpayers if people earn more and need less tax credit. What’s dishonest is that everyone’s tax credits fall automatically whenever their pay rises: there is no need for extra cuts to tax credits. When he writes that “lower welfare in return for a national living wage is widely recognised as a fair deal”, he pretends that his wage compensates for his cuts – but he leaves many far worse off.

Other long-exploded canards get an airing, as Osborne ignores the debunking by the Institute for Fiscal Studies of his claim that the benefit cap has sent thousands into work. The great majority, says the IFS, saw “very large reductions in income” and very few more went into work than the normal turnover.

But never mind the facts – how he relishes taunting Labour at the nadir of its fortunes, offering unfriendly advice: “Oppositions advance only when they stop blaming the public for their defeat and recognise that some of the arguments made by political opponents should be listened to.” True, Cameron earned the Tories’ route back by pledging himself to Labour’s child-poverty cause, only to ditch it in office.

Labour disarray over how to vote on last night’s welfare bill was inevitable in its current confusions. But colluding with fiddled facts and conceding unjust cuts would earn them no new support. If Osborne goes unchallenged in his full-frontal assault on the “unaffordable welfare state”, Labour is sunk.

Just as Blair and Brown shifted the conversation on to their positive new deal for the young unemployed, the new Labour leader will need the imagination to turn the spotlight on to the causes of welfare spending: lack of training and lack of house-building meaning 25 times more to be spent on the housing-benefit bill than on building.

Osborne shimmers with self-satisfaction. But YouGov’s polling on his budget by no means suggests a nation bent on battering the low-paid: fewer than half agree with freezing benefits; only 30% want the public sector pegged to a 1% rise; and only 24% want poorer students denied grants. Meanwhile, YouGov polling for the End Child Poverty group of 150 charities found 82% want child poverty to be a government priority.

In the throes of failure, some in Labour risk thinking they lost because of everything they stood for. In an excess of hubris, Osborne would be wrong to assume that too. The impact of these cuts will spill out – and he may find many are appalled.