Foreign Minister Winston Peters says New Zealand could have done better than it did in the free trade agreement it signed on Monday with China, and that is why his New Zealand First party won't support it.
He directed his criticism at China for not agreeing to a more rapid decline in tariffs but it also reflects on the deal the Government accepted.
"We could have done so much better," Mr Peters said last night.
He said Trade Negotiations Minister Phil Goff and his officials had done the best they could.
But as China had effectively had free trade with New Zealand for 20 years, it could have offered more.
Mr Peters said that because tariff removal would take up to 12 years and quota removal up to five years, the full benefits of the agreement would not be felt for up to 17 years.
"When the euphoria settles, people will start realising the seriousness of this situation."
Mr Peters said he would repeat the criticism he was making at home about the deal to his counterpart in China if he were asked.
"It is a trade matter handled by Phil Goff, but if I am asked I will give the same answer I give you today: there is not enough in it for New Zealand. We would have expected much, much more."
His willingness to criticise the deal appears to be at odds with the unusual arrangements under which Mr Peters is outside the Government as well as cabinet.
There is an "agree to disagree" provision in New Zealand First's confidence and supply agreement, but Mr Peters is also required to "speak for the Government on all issues" when overseas in his official capacity as a minister.
Asked about his responsibility to represent the Government and not New Zealand First he said, "It is very, very frequent that there are distinctions drawn when a foreign minister is offshore. He does not ever just parrot the same thing that might be the mantra of the last person who wrote a policy statement out of New Zealand."
For the Foreign Minister outside the Cabinet, the China free trade agreement is the biggest issue related to his portfolio on which he has differed from the Government.
But his party's opposition is no surprise to Labour, and no one on either side is expecting it to affect Government stability.
Labour is a minority Government ruling with the support of New Zealand First and United Future on confidence and supply issues and the abstention of the Greens.
Helen Clark said from Beijing that New Zealand First's announcement came as no surprise and she was "totally relaxed about that position".
"When Winston Peters was appointed Foreign Minister it was on the clear understanding that there would be a demarcation between his duties here and trade policies ... it was part of a whole confidence and supply package and he has completely honoured that package and those understandings at that time."
Asked how the Chinese would see the Government's Foreign Minister opposing the agreement, Helen Clark said: "The Chinese are well represented in New Zealand - they understand entirely the politics of New Zealand First and Winston Peters.
"Just as I have no surprise about anything that has happened in the last 24 hours from that quarter, nor will they."