Two hundred workers at Dendrobium went on strike last Friday and are not expected back to work until this Friday as they seek clauses in their enterprise agreements that limit the creeping level of casualization of the workforce.

Workers at Illawarra Coal’s Appin and West Cliff are expected to also negotiate for protection from casualisation in their agreements, which may lead to further stoppages.

CFMEU spokesman Bob Timbs said: “Around 20% of the workers employed on this mine are now contractors and that number is closer to 60% on other nearby mines. It's going to keep increasing unless we take a stand."

Timbs said the union had always understood the need for temporary labour during the mining boom, but in the past these extra staff would then transition into permanent, secure, full time jobs.

“Now South32 is taking advantage of the labour hire workers brought onsite during the boom. Instead of ensuring they are first in line to pick up permanent positions, they are keeping them in precarious, underpaid work," he said.

Illawarra Coal asset president Troy McDonald said the company has been working with employees and their representatives to develop a new agreement since late 2013.

“The mining industry, like many other industries in the Illawarra region, is facing a difficult business environment. Disruptive industrial action by the CFMEU would create further uncertainty for the company, its employees and the broader community,” he said.

McDonald will also have to contend with more longwall moves in the current financial year.

Three longwall moves are planned for the 2016 financial year (compared to two in the 2015 financial year), including one in the December 2015 half year.

This will take the gloss of last financial year’s record. Illawarra Coal saleable production increased by 19% (or 1.4 million tonnes) to a record 8.9Mt in the 2015 financial year.

An improvement in longwall availability and utilisation, and a 22% increase in washed tonnes from the West Cliff coal processing plant, underpinned record metallurgical coal production.

The 33% increase in June 2015 quarter coal production reflected an absence of longwall moves during the period.