Thousands of workers at the Sellafield nuclear site are to be balloted for strikes over a "completely unacceptable" 1.5% pay offer.
Around 5,000 members of the GMB and Unite unions at the site in Cumbria will vote in the coming weeks on whether to launch a campaign of industrial action in protest at an imposed 1.5% pay rise.
The GMB said most of its 3,000 members had rejected the pay offer, pointing out it is less than half the current 3.5% RPI inflation rate.
GMB official Chris Jukes said: "GMB's repeated requests for further talks have been ignored and the company has instead said it will impose its below inflation pay rise.
"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.
"Last year, Sellafield workers received just 0.25% extra in their pay packets, this year's offer of 1.5% is way below inflation again and would mean that yet another real terms pay cut for our hardworking Sellafield members after inflation has been taken into account.
"Members are also already looking at an increase of between 2 to 6% in their pension contributions, so this would be a double-hit on their living standards."
Unite regional officer Graham Williams added: "Low pay awards have been the order of the day for some time at Sellafield with the well-founded suspicion that this award dovetails with the Government's harsh pay restraint policies.
"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 Sellafield spokesman said: "We've offered our workforce an unconditional 1.5% increase this year - which is an increase to our wage bill of over £12 million year on year.
"After a ballot of their members, this has been accepted by one union, which has collective bargaining rights for over half the workforce, and rejected by two others who, between them, have collective bargaining rights for the remainder.
"Like all publicly funded organisations, we have to control costs and ensure we are delivering value for money for the taxpayer, so we're implementing a pay award which we feel is fair, reasonable and, most importantly, affordable."