A union official has also alleged the company plans to recruit a handful of former staff members to work as "strike-breakers" at the No. 5 blast furnace as rolling stoppages continue.

BlueScope refused to confirm or deny the claim, citing its policy not to comment on industrial relations matters.

Up to 500 steelworkers from three unions are expected to take part in a four-hour stoppage and mass meeting tomorrow morning as negotiations over a new enterprise agreement remain at an impasse.

It follows a week of smaller two-hour and three-hour stoppages across multiple departments.

Australian Workers Union Port Kembla branch secretary Wayne Phillips said unions were taking up the fight to stop BlueScope stripping away workers' conditions.

"The company has put a massive amount of false propaganda around advertising that the campaign's dead and people aren't participating ... which is totally wrong," he said.

"I think it's also time that our members were made aware that whilst BlueScope are crying poor they've just given their staff ... a 3 per cent wage increase plus a 9 per cent bonus."

He had "no doubt" BlueScope had approached former non-union employees to cover gaps at the No. 5 blast furnace during protected stoppages.

"I've been told that the company have gone around and contacted people ... who took the redundancy last year ... and they've asked those people ... to come in and work when we are off," he said.

"So in effect they've just gone out and hired ... strike-breakers."

Questioned further, Mr Phillips said an AWU delegate had been directly contacted by an ex-staff member, who had been approached by the company.

One blast-furnace worker, who asked not to be named, said some former staff had already arrived and managers had put the move down to "safety" reasons, which he rejected.

He understood the number was limited to four or five and that they would work as supervisors.