Over 600 jobs at employee-owned Hatfield Colliery in Doncaster are safe, for now, thanks to a fixed selling price for every tonne it produces, the owners say.
The deep mine has a contract with Hargreaves Services - which supplies power stations - until the end of 2015, a spokesman said.
The reassurance comes after rivals UK Coal announced it could close its two deep mines as it battles to stave off insolvency after being hit by cheaper imported coal.
The company, the largest producer in the country, is consulting on plans to shut Kellingley in Yorkshire, and Thoresby in Nottinghamshire, affecting a total of 1,300 workers. Some 50 jobs at its head office at Harworth, near Doncaster, are also under threat.
A spokesman for Hatfield said: “We think we can operate this pit profitably. The good thing is we have a contract to sell the coal, the quality is particularly good for power stations and there’s a lot of it.”
Hargreaves and ING Bank sold Hatfield to an employee benefit trust in December. Doncaster North MP Ed Miliband was involved in talks between unions and Hargreaves that led to the trust’s creation.
He said: “Workers at Hatfield colliery, now the last operational mine in South Yorkshire, took ownership of the site last year.
“Communities all over Doncaster have a long, proud tradition of mining so it was important to me that Hatfield’s future was secured and the jobs of the people employed there preserved.”
The pit was affected by a major landslide which wiped out railway tracks last year.
Prime Minister David Cameron said he would “do everything we can” to save UK Coal. He added: “We are talking to the company. There are obviously limits. This is taxpayers’ money involved.”