Up to 260 jobs may be lost as a result of British Steel's plans to close its coking ovens in Scunthorpe.
The company cited the need to make its operations more environmentally friendly, inflation, and an "unprecedented rise" in operating costs as causes.
Any cuts, according to the steelworkers' union, could have a "catastrophic impact" on steel production throughout the UK.
Coal is converted into coke in coking ovens, which burns at the higher temperature required by blast furnaces to produce steel.
A worrying sign for the state and future of the UK steel industry has been the closure of the ovens, which forces British Steel to import coke.
In addition to an "unprecedented rise in operating costs, surging inflation, and the need to improve environmental performance," British Steel reported that the company's energy and carbon bills increased by £190 million last year.
It stated that "decisive action" was required as a result.
Steelworkers' representative Alun Davies stated that the Community Trade Union would "not accept redundancies" and added that "nothing is off the table when it comes to protecting our members' jobs.".
The closure of the coke ovens, according to British Steel, "could have catastrophic effects on jobs and steel production at Scunthorpe and the UK as a whole," he continued.
