Union workers at the Sellafield nuclear site in Cumbria will be balloted for strike action over a pay dispute with the company.
GMB, the union for nuclear workers, will ballot 3,000 members, and the Unite union will ballot 2,000 members.
The unions argued the company has ignored repeated requests for further talks and imposed a "completely unacceptable" below-inflation pay offer.
Sellafield offered a 1.5 per cent pay increase in June, compared with the retail prices index (RPI) inflation rate of 3.5 per cent for the same month, which was rejected by 88 per cent of GMB members on site during a consultative ballot.
The strike ballot will begin next Monday, the 14th of August and will close on the 4th of September.
Chris Jukes, GMB senior organiser, said:
With Sellafield refusing to meet us, GMB has little alternative than to ask our members if they wish to take strike action to achieve a fair pay offer.
Unite regional officer Graham Williams said low pay awards have "been the order of the day for some time at Sellafield".
“There has been a sustained erosion of pay, and terms and conditions in recent years including a proposed new pensions’ package with reduced benefits and new starters employed on inferior conditions."
Government-led changes to pensions of nuclear workers mean two-third of Sellafield workers will have to pay an extra two to six per cent on their pensions contributions from next year, GMB said.
The management now needs to come to the table and negotiate in a constructive manner, otherwise possible future industrial action could bring Sellafield to a halt.
A spokesperson for Sellafield said the 1.5 per cent pay rise is an increase to the company's wage bill of over £12m year-on-year.
“Like all publicly funded organisations we have to control costs and ensure we are delivering value for money for the tax payer, so we’re implementing a pay award which we feel is fair, reasonable and, most importantly, affordable.”
The spokesperson added that a third union with collective bargaining rights for over half the workforce accepted the rise.