Up to 200 workers at Kellingley Colliery will be made redundant next month as its operators UK Coal continues with its plan to close the site.
The company will close the colliery by the end of the year, and it will write to workers at the site on June 19.
Those miners will lose their jobs as soon as they have finished the coal face they are currently working on.
Keith Hartshorne, National Union of Mineworkers’ delegate at Kellingley, said: “I think what these redundancies represent is the reality of what is actually happening to the pit.
“This is like the first proper step towards the closure of the pit - it’s devastating.
“We knew some workers were going to be leaving in phases throughout the year but this is like the beginning of the end of the coal industry.”
In March, the government said providing £338m to keep both Kellingley and Thoresby colliery, in Nottinghamshire, open until 2018 would not be value for money.
The Weeland Road site will close by the end of this year with the loss of 700 jobs.
Mr Hartshorne said: “We are due to finish the face we’re currently working on by July 10.
“But the redundancies tie in with whenever we finish on the current face so some of the lads could effectively end up working ourselves out of a job and being the victims of our own success.”
UK Coal first announced the managed closure plan last year.
Mr Hartshorne said there are around 600 workers still working at the site - 200 of which will lose their jobs as part of this wave of redundancies. No-one from UK Coal was available for comment when contacted by the Express.