The decision was taken at the union’s conference yesterday following what was described as “a full, frank and passionate debate about the union’s future”.

UCATT was formed in 1971 when woodworkers and painters & decorators and joined with the Amalgamated Union of Building Trade Workers (AUBTW) and the Association of Building Technicians.

The union said that the decision was taken “in order to preserve existing structures and to maximise the representation of construction workers in all sectors”.

UCATT will now enter into full negotiations with Unite, following which a vote on a transfer of engagements of all UCATT members will take place.

Brian Rye, acting general secretary of UCATT, said: “UCATT delegates listened to the arguments both in favour of remaining independent or a merger or transfer to Unite and decided that the best option for existing members and for all construction workers was a link up to Unite.”

Unite general secretary, Len McCluskey, added: “We welcome this chance to work with Ucatt colleagues on building a powerful, united union for construction workers where we can combine our might and expertise to get the best deal for this workforce.”