UCATT

Brian Rye, acting general secretary of the Ucatt union, which represents roadworkers, said the proposals for a roll-out would "make a dangerous working area twice as dangerous".

He enjoys strong support from many Labour Party members and has the backing of various unions, including the Communication Workers Union, train drivers' Aslef and construction workers' Ucatt.

Mr Corbyn has already received the backing of train drivers' union Aslef and construction workers' union Ucatt.

Last month the GMB and Ucatt unions and a law firm reached a separate settlement with construction companies.

The settlement with the GMB, Ucatt and law firm CGR was reached on 29 April but could not be announced until the Unite case was settled.