The Department for Work and Pensions (DWP) spent £697 million on IT for the scheme as of last December, according to top HM Treasury official Sharon White. Just £34 million of the money spent on IT so far will be used for the final system.
The survey adds to evidence that existing IT systems for Universal Credit are unworkable. The National Audit Office (NAO) published a report last November that warned systems "depend heavily on manual intervention and will only handle a small number of claims".
The PCS union polled about half of the 820 DWP staff currently working on pilots for Universal Credit, which aims to merge six benefits into one monthly payment. Just seven percent of respondents said IT systems for the new scheme are "adequate".
The DWP is currently following a 'twin track' approach of developing existing error-prone systems, but with a view to replacing them with a new digital solution, currently being trialled on first-time single claimants in Sutton.
Over four in five respondents said training was "less than adequate" to prepare them for the new benefit, while almost half said they were "stressed" or "very stressed" in their current role.
70 percent said staffing levels were less than adequate, while two-thirds said they were "frequently" asked to work overtime. 55 percent said they didn't think Universal Credit was an improvement for claimants.
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 undertrained 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."
The DWP was keen to downplay the significance of the PCS survey and claimed respondents comprised just 13 percent of 2,700 staff working on Universal Credit.
A spokeswoman said: "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."
However, a Channel 4 Dispatches programme due to be broadcast at 8pm today will provide further evidence that IT systems for Universal Credit are inadequate.
An undercover reporter who posed as an adviser trainee in a jobcentre in Bolton experienced problems with IT systems during the seven weeks he worked there.
For nine out of 20 days he had access to Universal Credit IT systems they crashed - once for the entire day, according to the Mirror.