Thousands of jobs of workers on Government computer contracts are to be axed over the next two years, union officials have been told.
The news - following last month's takeover of EDS by Hewlett Packard, the world's largest personal computer maker - was described as a "huge blow" to workers.
The Public and Commercial Services (PCS) union said 3,378 posts would be cut, warning it was bound to affect public services.
EDS has major contracts with the Department for Work and Pensions, the Ministry of Defence and other Whitehall departments.
Hewlett Packard warned last month that following the takeover it would cut 24,000 jobs across the world, although no details were given of where the axe will fall.
The PCS condemned the job losses, which it estimated worked out at one in five of the UK workforce, and said it would "vigorously oppose" any compulsory redundancies.
National officer Jim Hanson said: "Our worst fears have been confirmed. We feared 3,000 job losses for the UK, and the figure is even higher. For the last 18 months we have already seen job cuts in EDS with a voluntary redundancy exercise already in progress. It is disappointing that these figures have been made public before we have discussed how they have been arrived at."
PCS general secretary Mark Serwotka added: "This announcement creates further uncertainty with little or no detail of where the axe will fall and comes as a huge blow to the workforce in the time of economic turmoil. Our concerns about government IT contracts in the MoD and DWP will not be alleviated by this announcement. It's not just jobs that are at risk, but the delivery of public services that rely on IT services provided by the former EDS.
"We will be pressing management for more detail and assurances on compulsory redundancies and service levels in this period of massive economic uncertainty."
Hewlett Packard later confirmed that up to 3,378 jobs will be lost in the UK, adding: "Where possible, we will redeploy impacted individuals."
