Labour will support National's under-16s social media ban to select committee before the election, having earlier in the day indicated "no rush" to take a position.

Coalition partners Act and NZ First - who have long opposed the ban - have criticised the handling of the legislation, pointing to the prime minister's "lack of understanding" and National "panicking" in recent weeks.

Education Minister Erica Stanford - who had been leading the work - welcomed Labour's support, but said she would have liked to introduce it earlier.

She pointed to the time taken in discussion with Labour, despite her announcement of the bill's introduction to Parliament on Monday coming with no guarantee of Labour's support.

Labour leader Chris Hipkins said the party had discussed the matter at caucus on Tuesday morning.

"We will support that bill, and I've written to Erica Stanford conveying that support and encouraging the government to give the bill its first reading before the election, so that the select committee process can get under way," he said.

"The bill undoubtedly can use improvement. I'm not going to let a quest for perfection, though, delay progress ... we think through the select committee process there will be significant improvements ... the sooner we get that under way, the sooner that can happen."

Stanford had clearly not yet read the letter, finding out about Labour's backing from reporters on Tuesday afternoon.

"Oh, do they?" she said. "Well, they're in step with the rest of New Zealand, then, aren't they? Because they've just seen today what 80 percent of people on a Stuff poll [support it]. And we knew that, I'm out talking to parents every day."

Stanford said the timing of the bill's first reading would be up to Prime Minister Christopher Luxon and Leader of the House Louise Upston.

Peters, Seymour criticise process

Heading to the debating chamber on Tuesday, NZ First leader Winston Peters took issue with the way the bill had been promoted.

New Zealand First leader Winston Peters. Photo: RNZ

"It's not a government bill. That's my point. The second thing is, if they've answered all 75 or 79 of Labour's questions I'd be astonished - but then, the Labour Party has pretty low standards so I don't see that's going to be too much difficult."

The bill went through Cabinet and was introduced under the authority of a minister - which makes it a government bill, even if calling it a government "announcement" without the support of Act or NZ First may be a stretch.

"The National Party leader doesn't seem to understand. Don't blame the system. Don't blame the past. In all the other negotiations we've had and arrangements we've had, this has not happened," Peters said.

"It's a lack of understanding of how the system works, but then again we did say that he hasn't been around here long."

Asked how he would try to avoid such misunderstandings in future, Peters said: "Oh, we take people by the hand and take them through it very slowly".

Act leader David Seymour was similarly dismissive, saying the party would not necessarily campaign against the ban but would just point out that "this is not going to help and may harm".

"Clearly the National Party has been a bit panicked in recent weeks so, you know, we've got to give them a bit of relief from time to time.

"But certainly, you wouldn't want it to become normal that ... a third of the government, two of the three parties, disagree with something, and then they go it alone with Labour.

"I mean, there's not much point having a government on the right if your best friends are in Labour."

Stanford comments on tight timeframes

Stanford said it had been "always the intention" to introduce the legislation in time to progress it before the election "but we've just sort of run out of runway, unfortunately".

She was asked what the hold-up was.

"Well, I've been working with Labour for the last five months on this, answering multiple questions, having multiple briefings, showing them the bill multiple times, and here we are."

Stanford agreed it was a technical piece of legislation, saying that was "exactly why I made it available so many times, and my officials, and answering lots of questions".

"They have taken some time to get that understanding of the bill. Spend time with my officials, but we have done absolutely everything that has been asked of us. In fact, I've offered on multiple occasions, "Do you need more? Do you need more? So, I really wanted to get this across the line, and we worked really constructively together."

Labour's Media and Technology spokesperson Reuben Davidson earlier on Tuesday said Stanford's office had provided over 100 pages of documents on the bill, and it was the first time they had all the information.

Facing questions about whether she was suggesting Labour had caused the delays, Stanford did not answer directly.

"Well, I've been bending over backwards to make sure I got them everything they asked for," she said.

She was asked again.

"Look, I'm just saying they had lots of questions and they wanted to see the bill on multiple occasions, and then they asked for a copy of the bill which was a difficult thing to do, it had to get sign-off from the Attorney-General."

And again.

"Well, of course, we would have introduced it much earlier if we were able to."

Asked why had she introduced the bill on Monday when it was at that time unclear if it would have support to pass through Parliament, she said it was because she wanted to make sure the public could see "what we've been doing for the last year".

"That we take this issue really seriously, that they can unpack the bill, see that we've got a regulator - not only the age restriction, but also all of the things that we're requiring of social media companies to do - and that they can see we're putting ourselves in line with other countries."

Green Party co-leader Marama Davidson said a ban for young people was not the way to prevent harm, because the harm was felt by people of all age groups.

Social media platforms needed to be held to account rather than stopping certain people from using the platforms, she said.

Davidson was also concerned about the way the government went about introducing the law, with two of three coalition parties opposing it.

"They know it's not going to come in for a first reading this term, but this National government is introducing it, and I think - did they try to say that they had cabinet support? - they clearly do not, and I think we need to be really mindful of the mandate that governments hold."