Rachel Reeves says that Labour will reassess its commitment to Univeral Credit if it wins the next election.
She told the Sunday Times that the party will pause the project for three months, and call in the National Audit Office for a "warts and all" appraisal.
"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.”
The scale and ambition of Universal Credit, which aims to roll together six working-age benefits, has always raised eyebrows across Whitehall. The project has been negatively assessed by the Major Projects Authority - under the aegis of Francis Maude at the Cabinet Office - and the Public Accounts Committee, led by Labour MP Margaret Hodge. There are tensions both between work and pensions secretary Iain Duncan Smith and his department's permanent secretary, Robert Devereux, and between the department and George Osborne's Treasury over the failures of the scheme.
Hodge told the New Statesman in April: "The DWP seems to have embarked on this crucial project, expected to cost the taxpayer some £2.4 billion, with little idea as to how it was actually going to work.
“Confusion and poor management at the highest levels have already resulted in delays and at least £34m wasted on developing IT. If the department doesn’t get its act together, we could be on course for yet another catastrophic government IT failure.”