The date was confirmed by Unite general secretary Len McCluskey at a march in London today.

The ballot will be the defining moment in a wave of protests against plans by leading M&E contractors to quit the JIB agreement.

Unite has targeted Balfour Beatty as “ring-leader” of the seven firms looking to introduce a new pay and conditions deal.

McCluskey claimed today that clients spoken to by the union said they were taking a dim view of the industrial unrest.

He said: “Balfour Beatty will be the first of the rogue firms to feel the anger of its workers, who have already shown real guts in their battle to defend their livelihoods.

“Our members are enraged over the use of bully boy tactics to usher in an era of de-skilling across the sector as well and massive pay cuts.

“Balfour Beatty has been warned that its greed will bring mayhem to an industry struggling to steer a path through the recession, but they refuse to listen.

“The failure of the senior management at Balfour Beatty Engineering Services to withdraw the threats of dismissal has left Unite with no choice but to ballot members for industrial action.

“Perhaps the threat of strike action will bring Balfour Beatty to its senses and back to the negotiating table.”

Blane Judd, Chief Executive of the HVCA hit back and said: “We are deeply disappointed by Unite’s premature and unjustified decision to organise today’s protest.

“The claims by the Unite union that the new proposed agreement will lead to what it calls massive pay cuts and workers heading for the sack are total fiction.

“No one will take a pay cut – in fact 30 per cent will see an increase in their pay packets – and no one will lose their jobs.

“Unite demands that construction employers get back to the table for talks which is frustrating given that the union walked away in May and our door has remained open for six months.

“This new agreement will create job security and give apprentices and skilled staff a bright future which is something that British industry needs to see right now.”