Workers at the Ineos plant in Grangemouth have voted in favour of strike action.
Unite the Union said more than 81 per cent of those who voted supported the action, prompted by a company investigation into the union’s convener at the plant.
Of the 889 who took part in the ballot, 723 backed strike action, while 165 members voted against it.
Ineos said it was “disappointed” by the decision, and warned that any strike action could harm production at the site and cost jobs.
In an exclusive interview with The Falkirk Herald earlier this month, bosses said the petrochemical plant could close by 2017 if costs were not reduced.
Ineos also jointly owns the oil refinery with PetroChina.
The union said about 700 staff were employed at the chemical plant while about 500 worked at the refinery.
The dispute began after Ineos launched an investigation into its employee Stephen Deans.
Mr Deans, who has worked at the Grangemouth site for 24 years, also serves as the union’s convener and is chairman of the Falkirk Constituency Labour Party (CLP).
He was briefly suspended by the Labour Party in July following an investigation into claims of vote-rigging in Falkirk in the selection process to find a replacement for out-going Labour MP Eric Joyce.
Mr Deans was subsequently cleared by the party and reinstated as the local party chairman. A police investigation into the issue was also dropped.
Since then, Ineos has begun its own investigation into Mr Deans.
The company said it was investigating whether or not Mr Deans’ activities were in line with his role as an employee and a convener, and a decision based on its findings would be published on October 25.
Calum MacLean, chairman of INEOS Petrochemicals UK, said: “Ineos will not be bullied by the union’s behaviour. There cannot be one rule for union officials and one rule for everyone else.”
Mr MacLean added that Ineos had invested £1 billion at the site but that the petrochemical business continued to struggle.
North Sea gases – the raw materials for the site - are in decline and the current contractual supply agreement with BP expires in 2017.
The site is said to be losing in the region of £150m million per year and bosses say the pension scheme is already £200 million in deficit.