The deal, which includes a range of other benefits, was narrowly accepted in a vote by 3,000 workers, who operate under the National Agreement for the Engineering Construction Industry (NAECI).

The workers, who carry out essential repair and maintenance at oil refineries, power stations and pharmaceutical and petro-chemical plants, will see their wages increase by around £2,000 on average.  

Unite general secretary Sharon Graham said: “Due to the deal passing by a slim majority, Unite is now seeking to open negotiations for 2027 pay with the employers’ side as soon as possible. Unite never rests in the fight to keep improving our members’ jobs, terms and conditions.”

The workers initially rejected an offer of 3.6% that was imposed in February.

The offer was increased to 4.5% after Unite began the process of initiating industrial action proceedings for NAECI workers at sites across the UK, including EDF Torness, Sizewell B, Grangemouth, Drax, Stanlow ESSAR and GSK Montrose.

Unite national officer for construction Jason Poulter said: “Unite will continue to grow our industrial strength in construction, so that we can keep delivering wins for workers across the sector.”