In the last week of October the company forecast 6.2 million tonnes of output, but revised this down to 5.7-5.8Mt on Tuesday.

UK Coal’s Daw Mill longwall mine, the highest producing coal mine in the United Kingdom, is aiming to finish its current panel before Christmas to reach 3Mt for the year.

But the company said output had been affected by a larger dirt band than anticipated, meaning the coal will require extra washing and grading which will reduce the amount of saleable product.

At Kellingley, production restarted on October 26, but the mine’s recovery after the recent fatality has not been as swift as hoped.

UK Coal has marked down its estimates by another 100,000-150,000 tonnes, and said the total production impact of the tragedy had amounted to 300,000-350,000t.

The company now expects the deep mine to produce around 1Mt for the calendar year.

The last old panel at the Thoresby colliery is suffering from poor environmental and geological conditions.

The operation is mining through a seam-split, but progress has been slow.

“In particular, readings from dust-monitoring equipment on the face has required the company to reduce the daily man-hours worked on the face,” UK Coal said in its production update.

“We continue to mine through this seam-split, although at a slower rate than originally anticipated, and this slower mining rate is expected to continue for most of the rest of the year.”

The annual production estimate for the mine has been cut by 150,000t to 800,000t.

Tough geological conditions have also been experienced at the face of the Wellbeck colliery, also in Nottinghamshire.

UK Coal says these have been substantially worked through, but the delays have the mine looking at 1Mt output for 2009 instead of the previous 1.1Mt target.

Investigations into the fatality at the company’s Kellingley colliery in Yorkshire are continuing.