Unite said its members at Grangemouth in Scotland will walk out for 48 hours from 7am on 0ctober 20 over the treatment of Stephen Deans.
The site's owner Ineos has launched an internal investigation into Mr Deans, who was involved in the dispute over the selection of a Labour candidate in Falkirk.
Mr Deans, who is chairman of Labour's constituency party, was suspended by Ineos, then reinstated.
Unite accused Ineos of refusing to take the dispute to the conciliation service.
Unite's Scottish secretary Pat Rafferty said: "Unite has made every effort to pull Ineos back from the brink but at every opportunity this company has kicked our proposals for peace into touch.
"We have pleaded with Government ministers in Westminster and Holyrood and the joint owners of the Grangemouth refinery Petrochina to help rein in this reckless company before it's too late.
"A damaging strike may shut down the Grangemouth site, with serious ramifications for fuel production and supply throughout Scotland and the north of England."
Ineos recently launched a survival plan for Grangemouth, warning that the site will close by 2017 without investment and reduced costs.
The company said it was losing £10 million a month.
Officials said the investigation into Mr Deans will be completed by October 25.
Unite received an overwhelming mandate for strike action from the workforce, with 81.4% voting for walkouts and 90% for other forms of industrial action, on an 86% turnout.
A work to rule and overtime ban has been in place this week.
Mr Rafferty added: "The company can level whatever accusations it wants to at Unite and our members but we can only interpret their actions as a sign that they are determined to see strike action in an attempt to break the back of our union and run Grangemouth into the ground.
"Unite will fight back against attacks on our union and any attempt to impose devastating cuts on our members' jobs and hard-fought terms and conditions because that's what strong trade unions do.
"We will not negotiate with a gun to our head but Ineos can end this dispute tomorrow if they step back from the brink and begin to work with their employees again instead of against them."
Unite accused Ineos of using the dispute to try to force through changes to pay, pensions and terms and conditions.
A strike at Grangemouth in 2008 is estimated to have cost the economy hundreds of millions of pounds.
A spokeswoman for the Scottish Government said: "The Scottish Government is disappointed that strike action is now planned by Unite at Grangemouth.
"This news reinforces our fundamental view that this dispute can only be properly and fully resolved by negotiation between the company and the trade unions.
"We will now redouble our efforts to encourage negotiation to avert a strike, whilst taking forward contingency planning activity."
Scottish Conservative energy spokesman Murdo Fraser said: "This is a very unfortunate development at a time when there's already a question mark over the future of the plant.
"It's exactly the last thing it needs, and I'm extremely disappointed in this course of action by the trade union."
Ineos said it had "relatively high" fuel stocks at Grangemouth, adding it would look to bring in additional imports.
"We will try not to shut down any units unless we have to. We will do everything in our power to maintain fuel supplies," said a spokesman.
Energy Secretary Edward Davey said: "It's very disappointing that Unite has decided to strike. I urge them to call it off and for both parties involved to enter into talks about the long term future of the Grangemouth plant and reach a fair, sustainable resolution.
"We have been working closely with the fuel industry and Scottish Government to put robust alternative supply routes in place in the case of a strike, which means that motorists can carry on as normal, and other impacts will be kept to a minimum."