The Immigration Minister Chris Evans (Liberal) has announced a major shake up of the 457 visa scheme. It includes giving immigration officials more power to deal with the mistreatment of workers. There’s also penalties of up to 10 years in jail or fines of up to $110,000 for employers who rort the system.

CHRIS EVANS: I want a very clear message. People bringing workers into this country have rights and responsibilities and we're going to make sure they meet their responsibilities.

The average 457 salary is $90,000 a year. In Western Australia, the 457 average is $104,000. (The average salary in Australia is around $72,000.)

ALP vice president Tony Sheldon said polling showed it was "very likely" the coalition would take power in September and the union must try to blunt the conservatives' potential majority. (He is also secretary of the Transport Workers' Union)

He called for a shake-up of the 457 visa system, which is the type of visa given to skilled workers from overseas in Australia temporarily.

A coalition victory could see a flood of 457 visa holders come into Australia, Mr Sheldon said earlier in the day.