Twelve Tory MPs have signed a letter to Work and Pensions Secretary David Gauke, including Andrew Selous, former aide to universal credit architect Iain Duncan Smith.

Mr Duncan Smith’s “big idea” rolls six benefits into one, but Department for Work and Pensions (DWP) data show that 42 per cent of families are in arrears due the length of time it takes to get payments, stoppages or errors in the system.

Shadow work and pensions secretary Debbie Abrahams said: “Labour is again calling on the government to halt the roll-out of universal credit and remove the punitive elements of the programme."

Civil Service union PCS general secretary Mark Serwotka joined the calls, saying: “Cuts to DWP staff and resources must be reversed to give the department the means to develop a system that offers genuine help.”