Mani Saravanan had spent about two years working for Ironbark Fabrication when, in August, he travelled to his home town near Chennai for six days to get engaged. The wedding was set for December 6.

Mr Saravanan claims he began asking his employer in September if he could take annual leave in the first weeks of December.

The company refused. Mr Saravanan's parents and in-laws would not change the wedding date, and after filling out a leave form provided by a flatmate he travelled to India to get married.

While he was on his honeymoon, the company emailed to say he had been dismissed for abandoning his job and had lost his entitlements.

The Department of Immigration confirmed yesterday that the Moree firm was under investigation for the salaries it paid its overseas workers.

The Construction, Forestry, Mining and Energy Union has taken up Mr Saravanan's cause, in part because of his claim that Ironbark's entire production staff are employed on 457 visas.

Mr Saravanan said that of 28 staff, 25 were from India, two from Vietnam and one from Malta. A local source said that while all production workers were recent migrants or on temporary visas, about five or six employees had been given permanent residency.

Ironbark Fabrication would not answer questions yesterday.

The state secretary of the CFMEU, Andrew Ferguson, has written to the Immigration Minister, Chris Evans, seeking an investigation into why the Moree firm was hiring only 457 visa holders in a region with high unemployment.

Under reforms introduced last year, employers of 457 visa holders need to ''attest in writing that they have a strong record of, or a demonstrated commitment to, employing local labour and non-discriminatory employment practices''.

Ironbark was accredited as a 457 sponsor before the laws were introduced.

''The vast majority of employers do the right thing, but when foreign workers employed on subclass 457 visas are underpaid or exploited, it undermines confidence in the program,'' Senator Evans said.

Mr Saravanan, who is seeking a new job so he can remain in the country, said management had told him he could not take the requested leave at the start of December because ''everyone would want to''.