One thousand members of the Public and Commercial Services (PCS) union will go on a 48-hour strike at HP on Monday after the company refused to extend its job security guarantee beyond October.
The strike action will affect work at the Department for Work and Pensions, Vauxhall and the Ministry of Defence.
Jim Hanson, national officer at PCS, said: "We want long-term job security for all our members but HP would only commit to not carrying out compulsory redundancies until October."
Around 2,500 staff could be affected by the compulsory redundancies.
Hanson added: "We want them [HP] to lift the pay freeze that has been in place for the whole of 2009 and 2010, and for them to offer a pay rise."
Although 60 percent of the union's members received bonuses instead of a pay rise, Hanson said that 40 percent did not receive one, and the bonuses that were received were non-consolidated and therefore did not count for pensions and redundancy payments.
After a one-day strike in January, Hanson said the union had had "a couple of meetings" with the mediation organisation Advisory, Conciliation and Arbitration Service (ACAS), but HP "wasn't willing to move far enough."
"There was an offer of some money for some of our members," said Hanson. "But there were lots of strings attached."
These "strings" included HP wanting staff to work an extra half hour a week, or give up one and a half days of holiday a year, to qualify for a pay rise. It also wanted staff to join the HP appraisal scheme.
"Since 2008, when HP merged with EDS, they have had a programme of 25,000 job cuts. There's currently an exercise [of job cuts] and they have made about 500 people redundant in the current quarter," said Hanson.
HP did not provide a comment at the time of writing.
The dispute between PCS and HP has been going on since December 2009, when HP narrowly avoided a strike by union members by agreeing to sit down to talks at the eleventh hour.