Construction workers staged a series of demonstrations at sites across the UK today in the continuing row over pay and conditions in the industry.
Unions say that moves by a number of firms to introduce a new national working agreement for electricians, plumbers and other employees will lead to pay cuts and "de-skilling" of jobs - claims which are denied by employers.
Protests were held today in London, Cardiff, Glasgow, Liverpool, Manchester, Southend and Immingham, with some workers saying it was the biggest day of unofficial action in decades.
Unite members at Balfour Beatty voted for strike action but are being re-balloted after a challenge by the company, with the result expected in the New Year.
The union also plans to ballot members in other construction firms.
The Heating and Ventilating Contractors' Association (HVCA) said claims that pay would be cut and workers sacked if they didn't sign the new contract were "total fiction".
The organisation said it was working with seven firms to introduce a new single national agreement to replace five separate deals drawn up 40 years ago in the building engineering services sector.
Chief executive Blane Judd said: "No one will take a pay cut - in fact 30% will see an increase in their pay packets - and no one will lose their jobs.
"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."
The companies working with HVCA to introduce the building engineering services national agreement (Besna) are Balfour Beatty Engineering Services, Crown House Technologies, Gratte Brothers, NG Bailey, Shepherd Engineering Services, SPIE Matthew Hall and T Clarke.