A so-called "reasoned" amendment, it would stop the bill in its tracks, thwarting, for some time and perhaps for good, the welfare plans which the government, and especially Chancellor Rachel Reeves and Work and Pensions Secretary Liz Kendall, made a test of their own toughness just a few months ago.

A defiant Sir Keir Starmer has insisted he is not facing a confidence vote next week as Labour MPs prepare to rebel over welfare cuts.Some 108 backbenchers have signed an amendment that would halt the Government’s proposed changes – enough to threaten the Prime Minister’s majority.