The panel at the centre of commercial discussions contains 1.45 million tonnes of coal in the Deep Soft seam. Work on driving the roadways to open up the reserves has been taking place for several months, with the objective of having the face ready for production early next year.
The colliery has further substantial reserves in an adjacent seam.
UK Coal says a statutory notice advising of redundancies following a 90-day consultation period is being issued and it will continue to work towards a commercial solution within this period.
The company said Harworth mine experienced high methane levels in the first quarter of 2005 slowing coal extraction and also encountered extremely difficult geological conditions in the region of reserves being worked.
Following experience on this face, it was considered unlikely that further reserves could be economically extracted from this area of the mine.
“Everyone has worked tirelessly to find a solution. The performance and dedication of the workforce at Harworth has been exemplary. We have all worked extremely hard to save the colliery at a time of increasing demand for coal, and will continue to do so,” UK Coal chief executive Gerry Spindler said.
Located in the village of Bircotes, nine miles south of Doncaster, Harworth employs 310 people, and workings are the deepest in the country, with the No. 2 shaft used to wind men and materials, 1005m deep. The No. 1 shaft is 897m deep, with coal extraction centred on the Deep Soft seam some 1000m below ground.
UK Coal is Britain's biggest producer of coal, supplying around 7% of the country's energy needs for electricity generation.