Textile workers are worried the Government will sign an international trade deal that will end its procurement policy of buying New Zealand-made goods.
Opposition parties are already protesting about the terms of the Trans-Pacific Partnership (TPP) and want negotiations put on hold, now the Clothing and Textile Workers Union is seeking assurances its members won't be compromised.
A leaked document appears to confirm states signing up to the TPP could be sued by foreign investors over unfavourable laws, which has Labour and the Greens up in arms.
They've been assured by Trade Minister Tim Groser he won't sign away New Zealand's sovereignty but they're still calling for confidential details of the negotiations to be made public.
The textile workers say the document also indicates the Government's procurement policy won't remain intact, although clauses covering that are still secret.
"Most other trading nations have strong government procurement requirements," union secretary Paul Watson said.
"The United States requires its soldiers to be kitted out in American-made uniforms and Australian infrastructure projects often have a minimum local content provision."
He says it would be "reprehensible" if the government signed a deal that doesn't support local jobs.
The TPP is an extension of a free trade agreement between New Zealand, Brunei, Chile and Singapore which has existed since 2006.
Countries negotiating to join it are Australia, Malaysia, Peru, Japan, the United States and Vietnam.
The next negotiating round starts in San Diego on July 2.