A Labour Party bill to ensure contractors are paid the minimum wage has passed its second reading, despite government opposition.

National voted against it but United Future leader Peter Dunne, usually a government ally, continued to support it.

The Minimum Wage (Contractor Remuneration) Amendment Bill passed its second reading by 61 votes to 60 on Wednesday night.

The bill states people engaged as contractors have few of the protections given to employees under the Minimum Wage Act.

Labour's David Parker drafted the member's bill.

He said certain types of work, such as delivering pamphlets, were not subject to any minimum wage requirements.

When the work the deliverers do was broken down on an hourly basis, they were often earning less than the statutory $14.75 an hour, he said.

National MPs said the the bill was overly prescriptive and could make it difficult for low-skilled people to find jobs.

Labour, the Greens, NZ First, the Maori Party and United Future supported the bill.

National and ACT opposed it.

The bill still has to pass its committee and third reading stages before becoming law.