Next year, more than 10.4m UK households – more than one in three – will be left on average £150 poorer than they are today. Worse still, this loss will be concentrated on families already struggling, or even failing, to get by: those at or below the UK’s poverty line.

If you feel as though you’ve missed this headline, that would be no surprise: the news has barely attracted coverage, let alone reached the front pages, despite affecting some 26 million people.

What’s more, this year won’t be the first time those families have had money snatched from them: it is the fifth in a row. The reason isn’t a new tax, or unemployment, or universal credit. It’s the benefits freeze – perhaps the most important UK story that the media and politics persistently ignores.

Usually, each year, anyone receiving a working-age benefit – which includes working and child tax credits, which prop up low wages for households that need it – gets an increase in line with whatever the level of inflation is each September.

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This week, September’s inflation was announced at 2.4%, meaning that, on average, everything is 2.4% more expensive than it was a year ago. If the rate continues about that level, in the coming year you’ll need 2.4% more money just to afford to buy the same things. An increase to benefits in line with that amount would be what you would need just to stand still.

Ever since 2015-16, the Conservative government has instead “frozen” these benefits – a false term, given that in reality each year these families are seeing their incomes cut. For next year, the well-respected Institute of Fiscal Studies (IFS) estimates the average hit to income at £150.

But the cumulative effect of five years ends up much higher, at something in the region of £700 to £800, taken from families who were hardly finding it easy to get by in 2015. Even for those in work, the relatively fortunate ones, wages are yet to return to their pre-financial crash levels, meaning the government has imposed a devastating double whammy on the people least able to cope with it.

This does save the government a fairly significant amount of money. The IFS estimates the freeze next year will save about £1.6bn, instead of allowing benefits to rise in line with inflation.

Keeping that freeze year after year – as the Conservatives have done – compounds these savings, meaning the measure has now probably reduced government spending by about £8bn a year. Given the Conservatives’ relentless rhetoric about the need to improve Britain’s balance sheet, some might conclude that this was a tough but necessary step.

It is not. It has been a sustained and deliberate reverse Robin Hood operation, a calculated raid on the poor to allow the government to give cash away elsewhere.

Ever since entering government, the Conservatives have made a series of cuts to corporation tax, reducing government revenues by between £12bn and £16bn a year – far more than the money saved by the benefits freeze.

The government did not need to take this money from low- and middle-income families. It made a choice, and has all but escaped condemnation for doing so. What amounts to a large-scale robbery has received hardly a fraction of the scrutiny universal credit has (rightly) garnered.

Part of this failure does lie at the door of the media. Few in that sector come from backgrounds where these cuts are likely to bite, meaning the issue – despite affecting 26 million men, women, and children in the UK – feels distant and technical to many UK newsrooms.

It’s also the result of deliberate and sustained demonisation of benefits and the people who live off them – leading to the bizarre situation where it’s easy to cut benefits, but virtually impossible to tax fuel properly, even as we struggle with climate change and deadly air pollution.

But while the bulk of the political blame for this situation lies with the Conservative party that instituted the policy – which shows up the “compassionate Conservatism” branding as a hollow lie – these families have also been dismally failed by the Labour party too.

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Labour’s popular 2017 manifesto noticed the effects of the Conservative’s corporation tax cuts, and reversed them – as well as proposing various other tax hikes on the UK’s richest citizens. It then proceeded to offer to spend that money on a range of programmes, such as scrapping tuition fees, which would primarily benefit only slightly less rich families.

At no point did it offer to reverse the benefit freeze and offset its effects. It didn’t even contain the bare minimum: a promise to at least end the freeze and increase benefits to – or, better, above – the level of inflation.

Somehow the party of the workers forgot perhaps the most serious financial blight on millions of working families (and those looking for work) – and it has yet to make helping those families its stated policy.

In the UK’s ridiculous current politics, trying to enact a measure that would help 10 million families would be a tough political sell. But right now, no one is even trying to make it. As a result, 10 million families are being made poorer every year, and virtually no one in politics or the media has their corner. That urgently needs to change.

• James Ball is a former Guardian special projects editor, and the author of Post-Truth: How Bullshit Conquered the World