The Government has been accused of "hampering" an inquiry by MPs into the flagship Universal Credit benefit, which found that tens of millions of pounds had been wasted.
The Work and Pensions Select Committee said there remained "worrying uncertainty" over the computer system being used to bring in the new single payment for people who are looking for work or on a low income.
Universal Credit (UC) will replace six benefits, including jobseeker's allowance, income support, child tax credit and housing benefit, but a national roll out has been delayed.
The committee said the Department for Work and Pensions (DWP) needed to be "clear and frank" about the implications of the delays and called for revised estimates of costs to be published.
Computer problems meant that £40 million spent on software has had to be written off because it is of no further use, and a further £90 million has been spent on IT with a useful life of only five years, said the committee.
The IT problems were only revealed by a National Audit Office report last September, but the Government had known about them for at least 18 months, said the MPs.
"It is concerning that it took so long for the Government to acknowledge openly that there were problems with UC IT," said the report.
"The Government has hampered the committee's scrutiny of UC implementation by not providing accurate, timely and detailed information. It is not acceptable for the Government only to provide information about major policy changes when forced to do so by the imminent prospect of being held to account in a public evidence session."
Dame Anne Begg (Labour, Aberdeen South), who chairs the committee, said only 4,280 people were claiming UC by last December, compared with 1.22 million jobseekers allowance claimants, which showed the scale of the challenge facing the Government in trying to implement UC by 2017.
She said: "Whilst it is right to ensure that the system works properly before extending it, there is a difference between cautious progress and a snail's pace. Given the excruciatingly slow pace of roll-out to date, it is hard to see how the most recent implementation timetable can be met.
"Effective select committee scrutiny depends on the provision of accurate, timely and detailed information by government departments. DWP has not always provided this to the committee in the case of Universal Credit.
"The serious problems with UC came as news to us when the National Audit Office published its highly critical report last September, because the Government had not told us about its own concerns about UC, and the actions it had taken to address them, during 2012 and early 2013.
"On two occasions, the Government has made public the details about major changes to the timetable for UC implementation only when forced to do so by the prospect of oral evidence in front of the Committee. This lack of openness and transparency is not acceptable.
"We do not, as the Secretary of State (Iain Duncan Smith) suggested, want to run his department. We do, however, expect to have access to th e information we need to scrutinise it effectively."
Dame Anne told the Press Association that the DWP needed to be more open, and she agreed with the NAO, that there was a "good news culture" in the department.
Shadow work and pensions secretary Rachel Reeves, said: " The select committee is right to raise serious concerns about Universal Credit which has suffered endless delays and waste. Ministers promised one million people would be on the scheme by April 2014 but the latest figures show under 4,00 are.
"£131 million has been wasted already and on this programme which is so far costing an astonishing £161,905 per person. David Cameron must urgently get a grip of this crisis-hit policy before any more taxpayers money is wasted."
Public and Commercial Services union general secretary Mark Serwotka said: "The failure by the DWP to deliver an effective IT system is not just a terrible waste of public money, it is a disgrace that the department that constantly attacks benefit claimants through measures such as the bedroom tax and by portraying them as 'wasters' is, at the same time, squandering hundreds of millions of public money that should be spent on relieving poverty.
"PCS has no confidence that a new IT system will be any more robust than the first one. Only by urgently bringing the system back in house, and reversing the 25,000 DWP job cuts made since 2010 so that our members can manage their day to day workloads as well at UC implementation, will the Government stand any chance of averting a flagship failure."
A DWP spokesperson said: "Universal Credit and its IT systems are very clearly working well, with claimants receiving the new benefit and moving into work.
"We deliberately started in a slow, controlled and safe way, which the Committee itself has long recommended, so we can expand Universal Credit securely to more people.
"Universal Credit is on track and we will start expanding it to other Jobcentres from this summer."
The DWP spokesperson added: "We have made our plans to roll out Universal Credit very clear with regular updates.
"Furthermore, Universal Credit has come under significant scrutiny by Parliament, the NAO, the Public Accounts Committee and others. We do all we can to help these enquiries."