A routine software upgrade of desktop &to=http:// english.pravda.ru/science/19/94/379/14542_virus.html ' target=_blank>PCs at the Department of Work and Pensions has left 80% of the ministry's computers unable to send or receive e-mails.
A memo sent to jobcentres yesterday stated, "At this point there is no known solution. We are hopeful that some interim measures that are being considered may release some users from their current deadlock."
Staff were warned it could take another 24 to 48 hours to resolve the problem completely.
As a result of the failure, some cheques had to be issued by hand and the department admitted there were delays in some payments, reports Computer Weekly.
According to The Times, the department said today that after engineers from contractors EDS had worked through the night, the system was back to 95 per cent operational, but predicted delays to some new and amended claims with disruption expected for 48 hours.
Technicians from Microsoft were flown in from the Continent to join the staff from Texas-based EDS which runs the department's technology network as part of a £2 billion deal.
Officials downplayed the chaos, which coincided with renewed calls from union leaders for the department to drop plans to cut 40,000 jobs as part of proposals to shed 104,000 civil service posts.
Mark Serwotka, general secretary of the Public and Commercial Services (PCS), the biggest civil service union, said: "We would urge the government to think again and will be calling for a full inquiry into what is becoming yet another IT disaster."
Downing Street insisted the system was virtually back to normal after engineers worked round the clock all week to correct a blunder that left screens blank and forced staff to write some giros by hand.