More than 200 jobs could go at one of Cleveland's biggest employers.
Bosses at Cleveland Potash Limited have warned staff there will have to be 'significant' job losses.
The firm today unveiled plans to halt potash production at its Boulby mine in six months’ time as the move to the mining of polyhalite is completed.
A company statement says the move is likely to result in the loss of 'a significant number of jobs' and it is beginning consultation with its trade unions regarding the implications.
Managing Director Andrew Fulton stressed the move to polyhalite was vital to secure the mine’s future and that, despite the anticipated job losses, it would remain East Cleveland’s biggest employer.
The Boulby mine is the world’s only producer of polyhalite, marketed as Polysulphate, which is a multi-nutrient fertiliser containing sulphur, in addition to potassium, magnesium and calcium.
Mr Fulton said that the company would have an initial production target of one million tonnes.
He explained: "When we first announced our restructuring plans two years ago, we made it clear that potash reserves were close to the end and, at the point when they were exhausted, we would make the transition to polyhalite production, with the inevitable impact on our workforce levels."
The exact number of posts affected was not yet clear and the firm would be liaising with staff representatives over the coming months.
"At this stage, it is not possible to be precise regarding the numbers involved," said Mr Fulton.
" We are committed to keeping job losses to a minimum and will be discussing the implications with our trade union.
"However, job losses could be in the region of 230.
“We understand that this will be a difficult time for our workforce and their families. However, with the end of potash production, we have to concentrat on polyhalite production in order to ensure that we remain a viable business and are able to continue to make a major contribution to the local economy."