Labour wants Trade Minister Todd McClay to resign for misleading the public and the prime minister about possible trade retaliation by China over claims of surplus steel dumping.
Mr McClay has given three different versions of events since reports emerged a week ago.
While away in Indonesia last week, he initially urged the public to treat the report with caution, saying there was just no hard proof of any trade spat and the story was "extremely hypothetical".
A few days later, he acknowledged he had been personally briefed on the matter by his ministry the week before.
On Monday, he released a statement in which he said ministry officials had been dealing with the matter for the past few months.
"I want to make it clear today that there have been discussions and limited correspondence over the past few months as the Ministry of Foreign Affairs and Trade has endeavoured to assess the veracity of these reports," his statement said.
He has also apologised to Prime Minister John Key.
Mr Key said Mr McClay did initially give the wrong impression about whether government officials were aware of the reports.
"You know, the minister and I were at a press conference and the briefing I had was that the only discussions had been between the non-government agency and Zespri, and that was not correct," Mr Key said.
"He should have made both the media and myself aware of that."
New Zealand First leader Winston Peters said the government had got into the habit of changing its story.
"It's been happening for a number of years now. Just straight out denial or downplaying real concerns that have grown in many areas," he said.
"The prime minister should be, as he claims, all over such issues. Because if that arose in any administration, you'd expect the first person to be told, to be the prime minister."
Labour's finance spokesperson Grant Robertson said Mr McClay was clearly out of his depth.
A trade minister who did not appreciate the seriousness of possible retaliatory action by the country's biggest trading partner simply should not be in the job, he said.
"If John Key won't sack Todd McClay, the minister should do the right thing for New Zealand and resign," Mr Robertson said.
Labour leader Andrew Little told Morning Report it was another example of government miscommunication.
"Either the minister didn't know or if he did know didn't seem to be alerted to the significance of it and the prime minister either didn't know or wasn't alerted to the significance of it."
Mr Key said yesterday that Mr McClay had apologised for the miscommunication and he still had full confidence in his trade minister.
"I wouldn't expect his resignation, but I think it's a matter of good practice of the government to try and make that sure we're clear in what we're saying.
"I mean at the end of the day, if you look at the question you're asking 'is New Zealand at risk of retaliatory action' in the event that a complaint was lodged and MBIE decided to investigate that?'
"The assurances that we've had from the Chinese side is no we're not at risk of that."
Mr McClay said he was limited in what he could say as under the law any complaint made about steel dumping would remain confidential.
If an investigation was launched, it would be publicly notified.