TORY minister Iain Duncan Smith has cost taxpayers billions by cocking-up his cruel welfare policies, Labour revealed yesterday.

Independent research for the party shows his Department for Work and Pensions has caused the Treasury to spend £5 billion more than planned topping-up poverty pay during this parliament.

Shadow work and pensions secretary Rachel Reeves will tear into the “Tory welfare waste” in a speech today in the east London borough of Redbridge.

“This huge overspend is the result of the Tory government’s failure to tackle rising levels of low pay and job insecurity,” she will say.

“This failure means spending on in-work benefits, including housing benefit, is set to continue rising in real terms well into the next parliament.

“This is yet another example of Tory welfare waste.”

Ms Reeves will specifically highlight how 900,000 people have amassed a stunning combined wait of 118,000 years for sickness and disability benefits because of a shocking assessments backlog.

Mr Duncan Smith admitted yesterday to making mistakes in his flagship Universal Credit benefit system.

He said the scheme is being tested with families in north-west England but it is not expected to reach the rest of Britain until 2019 — two years after the original deadline.

National Audit Office chief Amyas Morse said that the minister “has reset universal credit on a sounder basis but at significant cost.”

But the body concluded it was too early to tell whether the scheme would deliver value for taxpayers.

Civil servants union PCS general secretary Mark Serwotka slammed the much-maligned scheme saying: “Universal credit has been marred by controversy, delays and high costs because ministers have tried to rely on it as a central plank of their ideological cuts to social security.

“It’s clear that the DWP is still a long way off being able to prove this scheme can be a success and that it will have the right staffing and resources to provide a proper service to people who are looking for work or need support.”