Capita staff in Birmingham are set to stage a walkout later this week in a dispute over what a trade union called "poverty pay".
Around 920 life and pension workers from across the outsourcing firm's UK offices will go on a 24-hour strike on Thursday.
The dispute follows what trade union Unite called a "derisory" pay offer which it claimed would have resulted in a real terms pay cut for 75 per cent of staff.
Capita had proposed a 1.5 per cent 'pay pot' which, according to the union, would have been distributed to staff through a performance-related grading system which it said "only serves to divorce pay increases from the cost of living".
Capital provides financial outsourcing services for clients such as Abbey Life, Aviva and Prudential.
National officer for finance Dominic Hook said: "Our members are fed up to the back teeth by enduring poverty pay while Capita accrues large profits on the back of their hard work.
"The strike will hit the services to a number of blue chip companies which may wish to put pressure on Capita bosses to come to a fair settlement.
"If Capita does not enter into constructive talks, more strikes are definitely on the cards, given the depth of anger of our members."
Unite said the strike followed an overtime ban by staff which commenced on June 3 and the on-call ban and standby ban, which started a week earlier.
The other Capita workers involved in the strike are based in Belfast, Bristol, Bournemouth, Glasgow, Manchester, Reading and Stirling.
A spokesman for Capita Life and Pensions said: "There has been no impact to clients to date and plans will be in place to ensure that we minimise any potential disruption to clients.
"We are disappointed that the pay proposal, which we believe is a fair and equitable one, has been rejected by around half of the Unite member employees of Capita's life and pensions business.
"Less than a third of the total workforce in our life and pensions business are Unite members."
