"We had problems with a routine software upgrade affecting desktop PCs," said a DWP spokesperson on Friday. "There have been delays with dealing with new or amended claims because many staff have not been able to access their systems. We have been working overnight with our suppliers to resolve the PC problems and nearly all users can now access their business systems."
The spokesperson confirmed that 80 percent of computers were brought down, and that its main suppliers are Microsoft and EDS.
Microsoft said that the issue has now been fully resolved, but was unable to provide any information on what caused the crash. EDS did not immediately respond to requests for comment.
"Microsoft is aware of the issue," said Microsoft the spokesperson. "We worked closely with our partners to help rectify the situation and to support the DWP."
The Public and Commercial Services Union (PCS), the union which represents civil and public servants in central government, said that the number of employees is around 130,000 full-time equivalents, with approximately 100,000 terminals, which would put the number of desktop computers affected at 80,000. A DWP spokesperson denied the figure of 100,000, saying that it employs only 80,000 staff, but did not have any figures on the number of desktop computers in operation.
The PCS said that the news of IT problems at the Department for Work and Pensions, calls into question the feasibility of axing 30,000 jobs on the basis of IT improvements.
"There was anecdotal evidence of Giros being written by hand and services in large parts of the country being severely limited as it emerged there had been major IT problems across the department since Monday," said a PCS spokesman.
Work and pensions secretary Alan Johnson has ordered an internal inquiry into the role of Microsoft and EDS, who run the ministry's network as part of a £2bn information technology deal, according to The Guardian.
By Thursday night, 95 percent of desktops were fully functional and the department claims that the impact on customers has been minimal.
This disruption is the latest in a line of government technology failures, which included the failure of the £450m IT project at the Child Support Agency and the collapse of the £500m Electronic Benefits Transfer System in August.
IT consultancy Avanade -- the joint venture between Microsoft and Accenture -- warned companies on Friday that the urgent need to migrate from Windows NT 4.0 before Microsoft withdraws support has caused problems for companies.
"With the imminent retirement of support for Windows NT4.0, the migration space has become increasingly frenetic over the past few months," said an Avanade spokesperson. "Avanade has identified that its customers are under increasing pressure to migrate quickly, but are concerned that with increased speed of migration comes risk."
For more reaction to the DWP debacle, read ZDNet UK's interview with Liberal Democrat IT spokesperson Richard Allan.