Thousands of workers at the Sellafield nuclear site are to start voting on whether to strike over a "completely unacceptable" 1.5% pay offer.
Around 5,000 members of the GMB and Unite unions at the site in Cumbria will be balloted in the coming weeks in protest at an imposed 1.5% pay rise.
Chris Jukes of the GMB said: "Pay at Sellafield for all but the top brass has failed to keep pace with inflation in recent years and it came as no surprise to GMB when our members voted by a ratio of nine to one to reject the Sellafield pay offer, which is less than half the RPI inflation rate.
"At the same time, Sellafield management have chipped away relentlessly at terms and conditions.
"In the circumstances, we now have no alternative but to ask our members if they are willing to take strike action in order to achieve a pay offer in line with inflation."
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."
The ballot results will be known in early September.