Opponents of the Trans-Pacific Partnership are planning a protest march in Auckland on the day trade ministers from 12 countries formally sign it.
The ceremony is set for next Thursday and the lobby group It's Our Future says the Queen St march will be "a symbol of massive public opposition".
Spokesman Barry Coates says thousands are expected to join the "loud and passionate" protest.
The Government today released a detailed analysis of the impact the TPP will have on New Zealand, saying the free trade agreement is expected to boost the economy by $2.7 billion a year by 2030.
Leading opponent Professor Jane Kelsey says the national interest analysis (NIA) is nothing more than an expanded version of previously-issued information.
"The NIA is a totally predictable cheerleading exercise that talks up the supposed gains and largely ignores the huge downsides of the TPP," she said.
Labour leader Andrew Little says the newly released analysis isn't actually that new.
"It merely reinforces the marginal gains New Zealand will make – less than 1 percent of GDP by 2030.
"This is a small economic gain and at the same time our sovereignty is being compromised."
He believes the analysis confirms the TPP will prevent future governments making laws in New Zealand's interest.
There are still questions about what the deal means for government-funded Pharmac and the future cost of medicines, he says.
While Labour has supported "genuine free trade agreements," Mr Little says "this goes far beyond just trade".
3 News / NZN