Announced nearly three weeks ago, Glencore said the three-week shutdown from mid-December was a considered management decision “given the current oversupply situation” plus it reduced the need to “push incremental sales into an already-weak pricing environment”.

Construction, Forestry, Mining and Energy Union national president Tony Maher called it a “compulsory stand down” that breached workplace agreements at some mines – making it illegal at those mines without the agreement of the workforce.

“Glencore’s decision to spring this on workers with only a month’s notice will catch some workers short of annual leave and force them to change holiday plans,” Maher said in response to the shutdown news.

“It demonstrates the arrogance of management, which could have negotiated with workers to find mutually suitable ways to reduce production – like letting workers take public holidays.”

The forced Christmas leave, which will run from December 15 to January 4 for most of Glencore’s Australian coal workforce, is also expected to take 5 million tonnes of coal out of global markets which have been consistently weak throughout 2014.

Maher even acknowledged support for Glencore’s motivation to eliminate coal supply and said “short-sighted overproduction of coal” had driven a cycle of lower prices and cost cutting.

“Glencore’s reduction in coal production will most likely be met by increases by other mine operators,” Maher said.

“We urge all coal mining companies to consider ways to look at ways they can reduce production and tackle the oversupply damaging the industry.”

With the shutdown poised to start in a little more than a week, a Glencore spokesman confirmed that it was going to plan at this stage.

“As we announced on November 14, we are moving ahead with planning for the production shut downs across our Australian coal operations for three weeks commencing mid-December,” he told ICN.

“We have communicated this decision, and the rationale behind it, to our workforce.”

CFMEU mining and energy division Queensland district president Stephen Smyth did not confirm whether any union disruptions or further responses to the Xmas shutdown were planned for any Glencore coal sites.

“Our national office is considering the options with this one,” he told ICN on Tuesday.

“We are still looking at it.”