Opposition to the controversial Trans-Pacific Partnership trade deal is being branded "ludicrous".

Thousands marched against the deal over the weekend, with rallies in 21 cities and towns.

But Trade Minister Tim Groser said some of the protestors are against any trade deal, while others are misinformed about the dangers.

"We will be unable to fight climate change, it will be the end of democracy and the sky will fall in. I'm sorry, these are really ludicrous claims," Groser retorted.

He said the opponents never ask how else New Zealand will pay its way in the world.

Labour's deputy leader Annette King said she's detected a change in Groser after Saturday's protests.

"He said that some things do keep him awake," King claimed. "So, I think already we are seeing a little bit of backing off from the government. I think, perhaps, because they are not looking at the deal they thought they were going to get."

Groser himself says it's still full steam ahead on negotiations.

But protest organiser Barry Coates insists Groser can't keep dismissing their concerns.

"Other trade agreements are not conducted in secrecy. Other trade agreements, they have the draft text made available, people can look at what's in it and then there can be a proper public debate."

Coates said the TPP potentially opens up the government to be sued by multinationals, and the public deserves a chance to debate it.

Professor of International Relations at Otago University Robert Patman said the protests were a strong message both to the government and to negotiation partners in the TPPA that New Zealanders are insisting on a deal that serves the country's interests.

"The stakes are high," Patman said. "This is a region where seventy percent of New Zealand's investment and trade occurs. Indeed, five of New Zealand's top ten trading partners are all in the TPP negotiations."

"In a sense, all of these economies are closely linked to ours. This is where our economic future is. It doesn't mean we have to accept any kind of deal, but it does mean we have some kind of stake in the outcome."