The government's flagship Universal Credit scheme is in "disarray" and is suffering from a lack of staff, poor training and an inadequate IT system, according to its own workers.
A survey of members of the Public and Commercial Services (PCS) union said 90% believed the scheme's current computing system which deals with benefits claims are not sufficient, with another 80% saying they had not received adequate training to prepare them for the new scheme.
Elsewhere, three quarters of the 400 people surveyed said working conditions were worse than in their previous role and four out of five adding they do not believe there is currently enough staff to cope with demand.
More than 50% also believe Universal Credit scheme - which is designed to make welfare simpler by combining six benefits, including Jobseeker's Allowance and Housing Benefit, into one single payment - is an improvement for workers.
Universal Credit, which was launched by the department of work and pensions secretary Iain Duncan Smith in April 2013, has struggled to be rolled out and its management has being previously criticised for being "extraordinarily poor".
MPs on the Public Accounts Committee also claimed the mismanagement of the project by Department for Work and Pensions had led to the waste of £140m ($211m) of taxpayers' money.
PCS general secretary Mark Serwotka said: "No one can trust Iain Duncan Smith to tell the truth about Universal Credit so it falls to the staff to expose this wasteful and politically motivated shambles for what it is.
"It has long been obvious that staff are under-resourced and under-trained and that universal credit is at risk of collapse. The DWP cannot keep burying its head in the sand and hope these problems go away because they are only going to get worse if nothing is done."
A Department for Work and Pensions spokesman said: "The PCS survey comprises of only 13% of our 2,700 staff working on Universal Credit. They chose to ignore staff in our Jobcentres when conducting this research providing a skewed unrepresentative sample of union members.
"The reality is Universal Credit is already transforming lives and our staff are passionate about the work they do."