Glencore has clapped back after the Australian Workers’ Union (AWU) joined the Electrical Trades Union (ETU) in publicly slamming the global commodities company over its pay offer to Townsville refinery workers.

The AWU accused Glencore of coming to the bargaining table with an offer described by workers as insulting, unsustainable, and a betrayal of the commitment they showed during months of uncertainty at the copper refinery.

As a consequence members had instructed the AWU to begin the process of taking protected industrial action, it said, echoing the stance taken by the ETU earlier this week.

A Glencore spokeswoman said today the company rejected the ‘inaccurate public comments’ unions had shared about the proposed offer made as part of Enterprise Agreement (EA) negotiations which began early this year.

‘Contrary to the inaccurate comments made by both the Electrical Trades Union (ETU) and the Australian Workers’ Union (AWU), Glencore has tabled a 13 per cent salary increase over four years,’ the company said in a written statement.

‘In the first year alone, we are proposing an effective 6 per cent salary increase for employees.

‘For both the ETU and AWU, who are part of the bargaining committee, to quote incorrect figures to media while we are still in negotiations is highly inappropriate and is a disservice to their members. We will continue to bargain in good faith and make a fair offer to our employees.’

Related: ETU slams Glencore pay offer for refinery workers

AWU Queensland northern district secretary Jim Wilson said the company was being economical with the truth.

He said a component of the pay rise was dependent on productivity, meaning members were not guaranteed the full amount and there was uncertainty as to how it would be determined.

Mr Wilson argued that the deal on offer would still leave many refinery workers significantly behind compared to the industry standard.

“And working in a copper refinery is a difficult job, especially in Townsville,” he said.

“It’s hot, it’s humid, you’re wearing bulky PPE – it’s a tough job.

“And so in terms of paying a productivity bonus, our members who have been there for a long time and who’ve experienced dealing with Glencore, they’re not confident that that’s a genuine offer.

“They believe that that’s part of Glencore trying to make the offer seem inflated so that it seems more appealing. And then when it comes time to determine productivity, it will be the company deciding, ‘actually, we’ll just keep that money for ourselves and send it back to Switzerland’.”

The Australian and Queensland governments in October announced they would put up as much as $600 million to keep Glencore’s Mount Isa copper smelter and Townsville refinery running for the next three years after the company sought support.

Glencore said it gratefully acknowledged the workforce’s backing in securing that government support.

‘To be clear though, even with the $600 million government support package, the smelter and refinery are expected to continue losing money, this must be factored into the EA negotiations,’ it stated.

‘Our focus is on trying to keep the smelter and refinery open so that our workforce continues to have jobs over the long term. We are committed to paying attractive salaries that are competitive and believe our offer represents a balanced approach which prioritises sustainable and long-term job security.’

While wheels have been set in motion towards initiating protected industrial action, Mr Wilson said no such action was likely to happen before the new year and it was hoped the parties could reach an acceptable outcome in the meantime.