Australian workers on the site said told Fairfax Media the safety equipment used by the men wasn't safe. One said the equipment looked like kids' toys.

White cards, required under the Occupational Health and Safety Regulations to ensure workers on construction sites comply, were issued by Sydney training group ABE Education three days after the visas were approved.

Fairfax Media has obtained copies of the visas, passports, the "white card" site safety certificate and letters of invitation from Hercules inviting seven Chinese workers to come to Melbourne to "assist with the installation of our Pit Type lift and slide mechanical carparking machine".

According to documents, it took 24 hours for the workers' visas to be approved. They then flew to Melbourne to work six days a week on a building site in Richmond, Melbourne.

Fairfax Media can reveal that the online training course offered by ABE is only available in English. The seven workers could only speak Chinese. It was purchased online for $58 after being "organised by someone in the office", Hercules managing director Terry Smith said.

A caller later made an inquiry to ABE's Dominic Ogburn asking him to explain how non-English speaking workers could complete the two- to three-hour course. He was told: "We've had quite a few people who are Mandarin do our course ... So there's nothing to prevent others from assisting them in going through it."

When asked if someone could do the course for them, Mr Ogburn replied: "Yeah ... We've got another company, a Chinese construction company, who have done the first one for them and then they hand out the answers to them and then they go online and then do it themselves."

He said he didn't want to be giving any "tips" but "we know that's what they [the construction companies] do because we say 'how the hell are they doing it in only an hour' but we know [laughs] that's what's going on. So you could do it and then write down the answers as you are doing each of the questions."

Mr Ogburn later denied he was advising companies how to rort the system. He told Fairfax Media: "It's not the correct interpretation. It's not what I was trying to convey." He said he had a strong compliance record.