The move follows an earlier decision to suspend the ballot in favour of fresh talks after over 4,000 members of the nuclear union Prospect overwhelmingly rejected a 2% offer in May, described as “the worst they have received in living memory.”

National Secretary Mike Graham said: “Our members have always sought to resolve this issue via negotiation but equally we are not prepared to sell them short. After nine intensive days of talks the company has still not been able to table an offer that comes close to our members’ expectations. The final offer rejected today amounted to 2% on basic pay and a potential 2% efficiency bonus.

“We recognise that Sellafield’s holding company, British Nuclear Fuels, faces government pressure to hold down pay in advance of the Nuclear Decommissioning Authority awarding the clean-up contract to a new parent body organisation.

“But our members should not be expected to tolerate an award that is below the market rate and relies unduly on efficiency bonuses because of behind-the-scenes interference from the Treasury and Department for Business, Enterprise and Regulatory Reform.”

Prospect members based at Sellafield, Risley and Capenhurst will, subject to the union’s National Executive Council’s approval, be asked to vote in favour of strike action as well as action short of a strike.