If there is a certain novelty value in the spectacle of Conservative backbenchers lining up to kick their own Government over benefits cuts, it will not last for long.

In fact, with changes axing child benefit for wealthier families set to come into force in January, the battle has already been fought and lost. But it is testament to the strength of feeling within the party that HM Revenue & Customs sending out informative letters on the subject is enough to reignite the dispute.

Nor is the outrage confined to the usual suspects on the Tory fringes, to those eager for any opportunity to destabilise a leadership considered perfidiously liberal. This time, the backlash is among mainstream Conservative MPs, many of them almost as aggrieved by tweaks to the welfare system that will hit the “strivers” so central to the prevailing Tory ideology as they are by David Cameron’s plan to legalise gay marriage.

And the current spat is only the beginning. The Chancellor is looking to cut another £10bn from an annual welfare bill already squeezed by £18bn. True, a slug of the extra savings could come from, say, a temporary freeze on working-age benefits – a move that might cause a storm on the left but is unlikely to provoke much resistance within the Conservative Party. But while such a move might yield perhaps £4bn over two years, it hardly comes close to the total.

What is needed is an altogether bolder approach – and that means precisely those perks most popular in the Tory heartlands. It means an end to the universal pensioner benefits that result in elderly millionaires receiving free bus passes and TV licences. It means further squeezes on the child benefit paid to wealthier claimants. It means a rethink of the tax relief on pension contributions, for example, or of tax-free savings vehicles such as ISAs.

None of the options is particularly palatable. But there is no other way to raise the kind of sum on which the Chancellor has his eye. After much argy-bargy, and some compromise, Mr Osborne won the first fight over child benefit. But that was only round one.