The mine is owned by Swiss company Glencore but operated by Leighton Holdings subsidiary Thiess, which has refused to comment on the job cuts.

Glencore says Mount Owen employs 400 people but the union says the relevant number is 270.

‘‘Cutting 60 production positions and eight tradespeople from 270 is a big cut, it’s 25per cent,’’ union official Peter Jordan said on Thursday.

Glencore confirmed the job cuts were related to the company’s February announcement that it was cutting Australian coal production by 15million tonnes this year.

The Mount Owen news coincided with the latest March employment figures, which showed a surprise fall in the national unemployment rate to 6.1per cent, a result doubted by some commentators.

Mr Jordan, northern district president of the Construction, Forestry, Mining and Energy Union, said the plan to cut jobs came after Glencore told Thiess was cutting this year’s output from Mount Owen by about 800,000 tonnes.

Mr Jordan said the union believed that most of the production cut could be met by operating the mine for six days a week rather than sacking workers.

The rest could be achieved by shutting the mine for a fortnight over Christmas.

Glencore shut its 16 NSW and Queensland mines for a fortnight this Christmas in a plan to cut production by 5million tonnes.

 ‘‘Talking to Thiess before Easter,  it seemed that this might be the way forward but they have obviously decided to go down the job-cutting route by calling for voluntary redundancies by next week,’’ Mr Jordan said.

He said absorbing the production cut through a new roster was ‘‘a double-edged sword’’ for the workforce because they would earn less on a six-day roster than they would if they worked seven days.

‘‘When Mount Owen began in the 1990s it was on a six-day roster to start with,’’ Mr Jordan said.

‘‘Instead, they are going for the job cuts. Bearing in mind that we’ve lost almost 100 positions in recent times, there’s unlikely to be  many volunteers for redundancy.’’

Mr Jordan said another Glencore mine, Ravensworth open-cut, had cut production by 500,000 tonnes.