The roll-out of the government’s controversial Universal Credit welfare reform has again been delayed in a decision costing half a billion pounds.

The Tories’ much-criticised flagship policy on benefits reform is now not expected to be fully introduced until September 2024, a fresh setback of an estimated nine months.

The Department for Work and Pensions (DWP) said on Monday that the delay was due to 900,000 more claimants than expected remaining on the legacy welfare schemes that UC is replacing.

UC has long been criticised for fuelling a rise in food bank use, as well as for numerous delays.

The DWP said the delay will cost an extra £500 million because there will be an additional 900,000 claimants receiving higher payments when they are moved to UC.

This is as part of the “transitional protection” to prevent those being moved on to the new system from losing out on payments, unless their circumstances change.

DWP minister Will Quince said: “Universal Credit is the biggest change to the welfare system in a generation, bringing together six overlapping benefits into one monthly payment and offering support to some of the most vulnerable people in society.

“It is right that we revisit our forecasts, and plan and re-plan accordingly, ensuring that the process is working well for people on benefits.

“Claimants will not lose money due to this forecasting change.”

UC was meant to have replaced six existing payments entirely in 2017 but it has been beset with problems.