Iain Duncan Smith's Universal Credit system could cost the British taxpayer an extra £1.25 billion as his failure to keep control of the project means it has spiralled out of control.
It aims to move all benefit claimants onto the online system by 2017, although this is a revised target as its completion has been held back by endless delays.
Labour has uncovered some more issues, claiming that some benefits, including free school meals and cold weather payments, have not been included despite Smith's claim that Universal Credit is all-inclusive.
The party believes that the Department for Work and Pensions has not accounted for the cost of these, and that they could end up adding more than a billion pounds to the bill.
There were supposed to be a million recipients of the benefit by now, but the true number is less than 12,000 as Smith has failed to manage his key policy properly.
This delay led UnemployedNet to estimate in February that, at the current rate of roll-out, it would be 2030 before all claimants were covered.
Universal Credit has been beset by problems from the outset.
Millions of people, particularly lone parents, would be better off on benefits despite the promise that it would 'make work pay'.
Last year it was estimated that 2.7 million people would struggle to budget with the move to monthly payments, leading to higher levels of debt.
The IT system has seen the waste of millions of pounds, being criticised by MPs and seeing a 'reset' - in reality, a new category invented to cover failure.
Rachel Reeves, Labour's work and pensions spokesperson, said:
“The Government has lost control of Universal Credit and millions in taxpayers’ money has already been written off.”