The Unite union official at the centre of the Grangemouth dispute has resigned from his job at the plant.
Stevie Deans was investigated by the company following his involvement in the row over the selection of a Labour candidate in the Falkirk constituency.
“The company has conducted a thorough investigation into Mr Deans’ activities over the last 18 months and made Mr Deans aware of these findings last week,” Grangemouth owner Ineos said in a statement.
“Mr Deans requested an additional five days prior to the final disciplinary hearing to allow him time to provide any further relevant information.
“The company was due to meet with Mr Deans again tomorrow but has now received his resignation.”
Unite said it would not comment until officials meet union members at Grangemouth.
The dispute between the union and Ineos was initially sparked by a row over the company’s treatment of Mr Deans, who is the Falkirk party chairman and Unite’s convenor at the Grangemouth plant.
Mr Deans and would-be Labour MP Karie Murphy were both suspended by the Labour Party as it investigated allegations of candidate-selection fixing in the Falkirk constituency earlier this year.
The investigation was closed last month after key witnesses withdrew evidence suggesting that they had been recruited to join Labour as part of a drive by Unite to cram the constituency party with supporters who would back its favoured candidate in a selection battle.
Both Mr Deans and Ms Murphy were reinstated as Labour members.
But Ineos proceeded with its own investigation into Mr Deans activities, prompting Unite members at the petrochemical site to ban overtime and opt to take other industrial action at the end of last month.
Ineos threatened to close the petrochemical side of the business but changed its mind after the Unite union accepted changes to pay, pensions and other terms and conditions.
The process of restoring the plant to full operation will take two to three weeks.