Workers at one of Scotland’s largest industrial plants are to ban overtime and work to rule, following a dispute over the treatment of a union official.
The Unite union said the action at Grangemouth Petrochemicals will start on Monday.
More than 1,000 staff are employed at the Ineos site.
The industrial action is aimed at disrupting and slowing down operations, Unite said.
The move followed an announcement that Ineos had asked the UK and Scottish Governments for grants and loan guarantees of £150 million to build a new gas terminal at the site.
The company said that, without new investment, it would close by 2017.
Grangemouth has been losing more than £10m a month and has a pension deficit of £200m.
The dispute with Unite centres on union official Stephen Deans, who was involved in the high-profile row with Labour over the selection of a candidate in the Falkirk constituency to replace Eric Joyce MP. Mr Deans was removed from his post amid claims he had been involved in a bid to manipulate the contest to select a Westminster candidate. The claims were later ruled to be unfounded but the union said Mr Deans could still be sacked.
Unite held a mass meeting at the Grangemouth site earlier tonight, where Ineos workers were due to discuss the potential escalation of industrial action.
Pat Rafferty, Unite Scottish regional secretary, said: “Unite has given Ineos management opportunity after opportunity to come to its senses and end the unfair treatment of Stephen Deans.
“Unite has announced action which will slow down operations from next Monday but the workforce are losing their patience and are ready to escalate the action unless the company ends its treatment of a loyal member of staff with 24 years’ service.
“Ineos is trying to spin this dispute into a fight over the future of Grangemouth – this is not the case. We have always been willing to sit down with the company and discuss the challenges facing the business. This dispute is about the unfair treatment of Stephen Deans who has already been cleared by the police and by the Labour party.
“We repeat our call to Ineos management to step back from the brink and end this wholly unnecessary dispute.”
Aside from the dispute over Mr Deans, union bosses are objecting to major changes for staff, which Ineos says are essential to prevent the plant from collapse.
The firm has put forward a survival plan for Grangemouth, saying it was willing to invest £300m to help build a new gas terminal to bring ethane from the United States.
It also plans to close a final salary pension scheme to help to stem losses.
Ineos says the average Grangemouth technician earns about £55,000 with extra shift work and bonuses, but that the cost of employing each is about £90,000 per year once the “unsustainable” salary contributions are added.
Ineos says change is essential.