Dwindling reserves and falling prices mean that around 140 miners will lose their jobs at the only potash mine in the UK.

The Boulby mine, situated close to Redcar, is the site facing redundancies in the latest blow to the region following the closure of its steel works last year that saw 3,000 people laid off.

However ICL had said that it would apply to extend the mine’s life by another 40 years, with its current licence to operate in the North York Moors National Park set to expire in 2023.

The facility employs about 700 people and only last November announced 220 redundancies and the elimination of 140 contractor posts.

The extraction of any remaining potash reserves will be slowed by Israel’s ICL as world prices have fallen by about 40% since the start of 2015.

The potassium found in potash is a key ingredient in fertilizer and ICL is now switching its focus to polyhalite, which is another form of the mineral containing other substances that help plants to grow.

It is made up of calcium, magnesium and sulphates, and can be crushed and spread on soil without further processing.

ICL has called it polysulphate and says that it will produce a series of products, with ICL’s executive vice president for potash, Peter Smith, stating: “When we announced the restructuring of the business last November we made it clear that, given the very limited level of economically feasible potash reserves, we had to move our focus to polysulphate production.”

Construction may start on a new $2.9 billion mine just south of Boulby to extract polyhalite in the next few weeks, with listed firm Sirius Minerals stating in July that it was near to raising the necessary funds for the project near Whitby.

Chief Executive, Chris Fraser, said that it had targeted a start date of September.