A bill aimed at stopping the exploitation of temporary workers.

Employed by labour-hire companies has passed its first stage of parliament.   

Labour MP Kieran McAnulty says "rogue" employers are using loopholes to fire people for things such as falling pregnant.

“They are involved in what is known as triangular employment arrangements. So they're hired by a labour-hire company, for example, and then placed on placement with a secondary employer. And that relationship, the absence of law around it, has led to those workers, in some instances, to being exploited.”

The bill passed with support from the Greens and New Zealand First.

National says it'll consider any changes made at select committee.