Australasian Meat Industry Employees Union representative Grant Courtney said the labour hire firm Pham Poultry has paid 10 workers at the Baiada chicken factory near Newcastle $20,000 in back payments.

But another 30 of the overseas workers were still owed $434,000 from the labour hire company, which recently went into liquidation.

"It is my understanding the $20,000 was for 10 workers engaged by the Baiada Beresfield plant," he said. "The Fair Work Ombudsman has cut a deal for the $20,000 to ensure these workers get paid something. But this company has waived its responsibility for another 30 vulnerable workers, who are still waiting on $434,000 in underpayments."

Mr Courtney, who is the AMIEU's Newcastle and northern NSW branch secretary, said the $20,000 payment was "a drop in the ocean" compared with what was still owed.

"We estimate that there are over 13,000 temporary international workers that are engaged in meat and poultry processing across the country and a large majority of those workers are being ripped off," he said. "Every international worker we talk to is being ripped off when it comes to award entitlements."

The union is seeking a total of $1.26 million in underpayments from four labour-hire companies, owed to 150 overseas workers on visas.

"We have four sets of proceedings against four labour hire companies that engage temporary international labour in the federal circuit court," he said.

A spokesman for Baiada poultry processing plant said the company was complying with its obligations under the Fair Work Act in relation to employees at its Beresfield site, which was under investigation by the Fair Work Ombudsman in 2011.

"Any allegations or assertions of impropriety against our employees are false," he said.

The Fair Work Ombudsman investigated complaints from the employees, aged between 21 and 30, who were being paid between $11.50 and $13.50 an hour for shifts of up to 20 hours.

The workers claimed $100 a week was taken out of their wages to pay for accommodation in crowded share houses.

The workers, from Hong Kong and Taiwan, were in Australia on 417 working holiday visas.

The Ombudsman's inspectors were told female workers were paid $11.50 an hour to wrap, label and pack trays of meat. Male workers were paid $12.50 an hour and workers using a mincer were paid $13.50.

The Ombudsman found 10 employees had been underpaid a total of $20,250 between May and October 2013 and that they should have been paid between $16.50 and $39 an hour.

Ombudsman Natalie James said the entire meat processing industry was under review and findings would be reported publicly.