The Engineering Printing and Manufacturing Union says changes to legislation that make it easier for New Zealand companies to win public sector contracts do not far enough.
On Wednesday, the Government announced changes to procurement rules to make the tendering process more consistent across the public service.
The rules take effect on 1 October and replace 44 pieces of legislation and guidelines which set out how government contracts should be awarded.
The changes include giving businesses more information about government procurement plans and giving them a longer time to respond to tenders.
But the EPMU says the new guidelines fail to require any preference or support for New Zealand-made goods and services.