Labour will halt Iain Duncan Smith's universal credit programme if it wins the election, Rachel Reeves has said.
The shadow work and pension secretary said the programme would be paused while the National Audit Office (NAO) conducts a "warts and all" review.
"Universal credit is in a bit of a mess, to put it mildly," the shadow work and pensions secretary told the Sunday Times.
"If it carries on like it is, it's going to fail. Next year, if I'm secretary of state, we're going to have a pause and let the NAO do a review."
Reeves said she was still supportive of the scheme on principle, but that she would take a hard-headed view on the chances of the project being delivered without disproprtionate cost to the taxpayer.
"If we thought this was a totally ridiculous idea we would just say we're going to scrap it," she said.
"Given that work has been started and a lot of money has been spent on it, we hope the costs of continuing with it will be smaller than the benefits of not proceeding with it."
"We're not going to go in with a preconceived notion that we are going to proceed at any cost, which seems to be Iain Duncan Smith's approach," she added.
"This is his baby and he's not going to abandon it, however bad things get."
One by one, the £18 billion scheme's supporters have fallen away as new financial and IT problems have emerged, leaving the work and pensions secretary looking isolated.
The NAO previously warned that there was no "detailed view of how universal credit is meant to work".
The government's Major Projects Authority confirmed the programme needs a "reset" while the public accounts committee has criticised almost every aspect of it.
"Its implementation has been extraordinarily poor," chair Margaret Hodge said.
"The failure to develop a comprehensive plan has led to extensive delay and the waste of a yet to be determined amount of public money.
"£425 million has been spent so far on the programme. It is likely that much of this, including at least £140 million worth of IT assets, will now have to be written off.
"The management of the programme has been alarmingly weak. From the outset, the department has failed to grasp the nature and enormity of the task, failed to monitor and challenge progress regularly and, when problems arose, failed to intervene promptly."
Duncan Smith has gone out of his way to prevent information about the programme becoming public. The DWP is continuing to block the publication of reports into the failure of the scheme at the upper tier information tribunal.
The department aims to introduce universal credit to 90 jobcentres in the northwest by the end of the year.