Workers at Tanfield Engineering Systems in County Durham have agreed to another strike - this time for a full fortnight.
As the company prepares to launch its new electrical vehicle under fanfare at a trade fair in Birmingham today, 122 workers are on the picket line for their second full week of strike action over pay.
Last night Tanfield management hit back - threatening to restructure the business if a pay deal is not agreed.
Union representatives met with management last Thursday but the meeting ended in stalemate.
The workforce at Tanfield, who are also sticking to an overtime ban and are represented by the Amicus, GMB and T&G unions, have said the 2.5% they have been offered by parent company Tanfield Group is "insulting" when the RPI measure of inflation is running at 4.6%.
The workers say they are particularly angry with the pay offer at a time when Tanfield Group as a whole is prospering so conspicuously.
The company is now largely based on a huge site at Washington, next to the A1 motorway, where it produces electric vehicles and aerial access platforms.
Yesterday the company unveiled new blue chip orders for its electric vehicles, and Tanfield Group as a whole is targeting £100m sales this year - up from £40.9m last time.
Amicus regional officer Dave Telford said: "We had a mass meeting this morning and the decision was taken to increase action - to step it up.
"There will be a two-week strike at a date to be determined."
Mr Telford said the unions were prepared to negotiate.
He said: "We got round the table last Thursday, but there was no movement from the employer, so we had no option but to continue the action.
"We remain available for talks - they have our pay claim and we have said it is negotiable. Their offer of 2.5% is well below the cost of living."
A Tanfield Group spokesman said: "We still believe 2.5% represents a fair pay increase and would make them (the TES workers) among the highest paid skilled workers in the North-East for their jobs."
The spokesman claimed 2.5% was the maximum increase the group could offer the Tanfield Engineering Systems workforce.
He added: "It would be irresponsible to divert profits from one section of a business to subsidise the wages of another division.
"The other option would be major restructuring of the engineering division. It's very early days at the moment but if there's not a way forward we would have to look at all options to maintain that business's profitability."
Staff at the Stanley base of TES work from fabrication and manufacture to assembly of electronics, pneumatics and hydraulics. Customers include BAE Systems, Caterpillar, ICI, Rolls Royce and Toyota.