Union Unite leaders said MJN Colston has written to its 500-strong workforce saying it will no longer be a party to the planned move to quit the agreement and introduce the new BESNA deal.

Unite is hailing the decision as a major victory in its campaign to fight plans by the rebel eight to revolutionise industrial relations in the M&E sector.

National officer for construction, Bernard McAulay, said: “We are pleased that MJN Colston has seen sense and returned to the JIB.

“The last few weeks has seen large protests across the country. Our members are clearly angry at having their agreements torn up and being threatened with dismissal if they do not sign up to new inferior terms and conditions.

“The JIB was set up forty years ago to end industrial unrest and introduce stability into the sector. Now because of the bullying way these companies are behaving we are seeing instability creeping back.

“We hope that Balfour Beatty, Crown House and the rest come back to the negotiating table so that we can move forward in a sensible and constructive way.”