Nuclear power plant workers from a second trade union have backed strike action in a pay dispute.

Unite the union confirmed 85.5% of its 460-strong membership at the Dounreay complex in the Highlands have voted in favour of a walkout.

With a turnout of 82.3%, the union said strike action now appears to be “inevitable” amid a row over a 4.5% pay offer backdated to April 2023.

It follows the announcement that 85% of around 450 workers represented by GMB Scotland backed industrial action at the nuclear plant.

Workers are tasked with cleaning up the Caithness complex, which operated as a nuclear plant from 1955 until 1994.

It is now operated by Nuclear Restoration Services (NRS) and is in the process of being decommissioned for future generations.

The NRS has said it is “disappointed” by the votes for strikes but it hopes industrial action can be avoided.

Sharon Graham, Unite’s general secretary, warned the NRS it has a final opportunity to resolve the dispute.

She said: “The Dounreay workforce have overwhelmingly backed industrial action because NRS has repeatedly failed to make them a fair pay offer. At the same time, the company has found the time to feather the nests of its directors.

“Unless NRS quickly gets back around the negotiating table to make our members an offer they deserve, then industrial action will be inevitable.

“Unite will fully support our members at Dounreay power station in the fight for better jobs, pay and conditions.”

The 4.5% offer was previously rejected by 95% of Unite members in an earlier consultative ballot, with the union arguing it amounts to a real-terms pay cut due to inflation.

Marc Jackson, Unite industrial officer, said: “NRS has basically strung our members along since January 2023 and they have simply had enough of the company’s games.

“There is a final opportunity to make our members a serious offer or any industrial action will lie at the doors of directors who have so richly remunerated themselves while ignoring the workforce.”

Keir Greenaway, GMB Scotland senior organiser, said on Thursday the union’s membership at Dounreay backed strike action with a turnout of 85%.

He said: “Managers insist they are bound by civil service rules but apparently can pick and choose which rules to follow. They seem far more relaxed when it comes to their own pay, for example.”

An NRS spokesman said: “We are disappointed by the result and remain committed to working with the unions to find a resolution that is fair and affordable.

“While we hope industrial action can be avoided, we will now implement contingency plans to ensure minimum staffing levels are in place to maintain safety, security and environmental protection during any period of disruption.”