More than 1,000 UK Fujitsu IT workers belonging to the Public and Commercial Services (PCS) or Unite unions are to strike on 19 September in a dispute over pay.
Fujitsu works on a number of government contracts, and the action could affect HM Revenue & Customs, the Ministry of Defence, the Office of National Statistics and the Driver and Vehicle Licensing Agency.
The National Outsourcing Association has advised the government to reassess its disaster recovery plans in light of the strike.
The joint action will take place for 24 hours from midnight on 19 September, and involves union members based at various locations throughout the UK, including Manchester.
Fujitsu has met or exceeded its performance on government contracts, according to a joint statement by the unions, but has refused to give staff a decent pay rise.
Some Fujitsu staff earn just £13,500 a year, less than some senior managers receive in annual bonuses, the statement said.
Fujitsu is also breaking previous staff agreements covering issues such as union recognition, pay, benefits, pensions, redundancy and redeployment, the unions claimed.
"Such a pitiful pay offer to workers, who are paid less than what some senior executives pocket in bonuses alone, is an insult," said PCS general secretary Mark Serwotka.
"Our members may work for Fujitsu but they are supporting essential public services, so ministers must recognise that they have a responsibility for what happens on behalf of their departments."
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