Foreign workers on a building site in regional New South Wales are being exploited and paid as little as four dollars per hour, the nation’s leading construction union says.

The Construction, Forestry, Mining and Energy Union says 13 Chinese and 16 Filipino workers employed by Taiwanese company Chia Tung Development Corporation which is installing a pellet feed mill Manildra Group’s Ethanol Plant in Bomaderry have been working between ten and eleven hours per day, seven days per week and taking home between $40 and $100 per day – an equivalent rate of between $4 and around $10 per hour.

Moreover, the union claims the workers – whom it says have also not received overtime allowances or penalty rates – told its officials during a site visit that their situation is part of a national ring that may reach into other parts of regional New South Wales as well as Queensland, Western Australia and Victoria.

“We’re getting tip-offs also from the public in a variety of different areas as well and we have a fairly substantial list of places where we know where this is going on and we’re going to investigate every part of it,” union State Secretary Brian Parker told the ABC, adding that the union was aware of two other locations in New South Wales where this was allegedly happening.

In a statement, Manildra Group said Chia Tung provided their own workers for the site and added that it was unaware or any situations whereby workers were being exploited but said it was taking the matter seriously and was making enquiries with its contractor.

The latest claims come amid ongoing debate about foreign worker visa programs in Australia, which industry lobby groups say provide an essential source of labour to fill skills gaps but unions claim are rife with abuse.

Earlier this month, a Department of Immigration and Border Protection paper set out proposals for a new type of visa which would allow companies to bring in foreign workers for up to a year without the workers having to meet strict language and skill requirements under the existing 457 regime or the employer having to meet requirements to conduct market testing prior to prove that no local labour was available to suitably and adequately perform the role in question.

The proposal was welcomed by employer groups but slammed by unions and some professional associations such as Engineers Australia – the former saying requirements of the existing 457 regime were too onerous for short-term contracts whilst the three to six months allowed under an existing category 400 visa was insufficient to meet the requirements of many temporary roles and the latter fearing the move would see foreign workers swamp the market for skilled professionals.

In a statement, the CFMEU says it is working with workers at the plant – most of whom it believes are on subclass 400 visas – to recover their entitlements, adding that making this type of visa more easy to obtain would lead to more further system abuse.

“Instead, the government should stop employers like this from rorting the system, banning the worst offenders from taking on migrant workers, and put in place proper labour market testing to make sure that local workers can get a start and don’t get undercut,” the union says.