There can rarely have been a better fit for Ebenezer Scrooge than Iain Duncan Smith. He told Andrew Neil on the BBC’s Sunday Politics that he wants child benefit limited to a family’s first two children. It would save money and prompt “behavioural change”.

For a country already failing to replace its population, with just 1.9 babies per woman, dissuading child-bearing is a mistaken and nasty ambition. When Scrooge asks, “Are there no workhouses?” he is told that many would rather die than go into one. “If they would rather die,” Scrooge replies, “they had better do it, and decrease the surplus population.”

Duncan Smith himself has four children. So do Boris Johnson and Sajid Javid. George Osborne, David Cameron, Philip Hammond, Grant Shapps, Jeremy Hunt and Nick Clegg all have three, so this government is far more fecund than the general population. But people like them are not the target of this “behavioural change”. What the government wants is fewer oiks.

Back in 1974 Keith Joseph destroyed his Tory leadership hopes with this speech: “A high and rising proportion of children are being born to mothers least fitted to bring children into the world … Some are of low intelligence, most of low educational attainment. They are unlikely to be able to give children the stable emotional background, the consistent combination of love and firmness … They are producing problem children … The balance of our human stock, is threatened.”

Sir Keith had four children but apparently they didn’t threaten “our human stock”. These days, what he said might be less controversial: it’s an everyday rightwing press platitude.

Some themes deep in the heart of Toryism just never go away. Up they pop, over and over. Control the lower orders, stop them breeding, check their spending, castigate their lifestyles. Poking, sneering, moralising and despising is hardwired within Tory DNA.

The desire to extirpate the poor goes back a long way. In 1913 the eye-opening report, Round About a Pound a Week by Maud Pember Reeves and her group of Fabian women (republished by Persephone Books) detailed the household accounts of mothers trying to keep their families on the average £1 manual wage. The report’s irrefutable evidence showed that wages were too low to live on, puncturing the perpetual myth among the comfortable (then as now) that the working classes were “bad managers”. In fact, these mothers scrimped every farthing, maximising calories in bread and dripping.

I was reminded of that book because Pember Reeves wrote angrily of middle-class assertions that no one should have children until they can afford them. She pointed out that working families would never have any if they waited for that day – but, of course, that is what Duncan Smith wants.

Pember Reeves was even more scathing about the well-off who preach what she calls contemptuously “the gospel of porridge”. Ah, porridge! Right on cue, up popped Lady Jenkin, wife of Tory MP Bernard Jenkin, last week: “Poor people don’t know how to cook. I had a large bowl of porridge today, which cost 4p.” She was presenting the Church of England report which found that 4 million people are going hungry.

The Mail hurried to her home and she told them how to cook a three-course meal for 57p – soup, rice and lentils, and banana and custard powder. The Mail’s verdict? “Simple, filling and very tasty.” So here we are, back with the argument that never changes: poverty is caused by fecklessness and dependency, not by sub-survivable rates of pay.

The baroness had no wise tips for how a family on the minimum wage should procure a Christmas present for a child: home-knitted socks? Easier for people such as her to ignore the steep fall in real wages, or that only one in 40 net jobs since 2008 has been for a full-time employee, according to the TUC. Easier to overlook Monday’s report from the Office for National Statistics showing the bottom 10% have suffered much higher rates of inflation than the well-off, spending more on food and fuel.

Of the unthinkable £48bn cuts Osborne announced in his autumn statement, the only specific one that he, Duncan Smith and the others keep crowing about is another £12bn to be cut from benefits, confident that Tory polling finds welfare cuts still popular.

But the tide may be on the turn: Osborne may have called it wrong this time. On Wednesday the Commons votes on a Labour motion to repeal the bedroom tax. The last attempt was voted down by the Lib Dems, but those eyeing their seats would do well to relent this time. The bedroom tax feels like the tipping point, where the public understands what cuts mean – half a million families reduced to penury or evicted, a third of them disabled, uprooting parents from jobs and children from schools. That £7bn promised tax cut for higher earners looks less like a winner every day.

The Institute for Fiscal Studies predicts that on present cuts alone, a third of children will have fallen into poverty by 2020. Another scandal: those newly struck down by sickness or serious accidents are lost in a Department for Work and Pensions penniless limbo, waiting for Duncan Smith’s personal independence payments. Last month 323,000 were waiting, according to the works and pensions committee – families in utter destitution, average wait about 60 days, due to DWP chaos. As the Church of England report revealed, the most common reason for using food banks is benefit delay and “sanctions”. Local benefit offices have tough targets for throwing people off benefits, not for how many get jobs.

The Tablet voted Duncan Smith one of the most influential lay Catholics in the UK in 2010. But an influence for what? He will no doubt be singing lusty carols in church this Christmas, most concerning the poor – Good King Wenceslas, perhaps? “Ye who now shall bless the poor, shall yourselves find blessing”, though poorer children have taken the hardest hits.

Listening to children in the wonderful London Symphony Orchestra Discovery Choir at the Barbican, I could only wonder how anyone in this government – religious or not – can cope with the imagery of Christmas. Do they hear the songs about welcoming new babies into the world, the poor child in a lowly cattle shed and rich men bearing him gifts, with at least a twinge of shame?

Scrooge is the great redemption story, but it might take more than three ghosts to see Duncan Smith, Osborne and Cameron recant their vendetta against the poor. If anyone spots them singing carols, please tweet.

• This article was amended on 16 December 2014. An earlier version said the Tablet had voted Iain Duncan Smith the most influential Roman Catholic. In fact he came 10th on its 2010 list of the most influential lay Catholics in the UK. It was further amended on 19 December 2014 to clarify a reference to research by the TUC and change a related hyperlink.