Labour may adopt Green MP Sue Bradford's anti-smacking bill as a Government measure to speed it past a parliamentary roadblock.
Deputy Prime Minister Michael Cullen yesterday refused to rule out the notion, saying he preferred not to comment.
Public opinion polls are strongly against the bill, and hundreds of protesters took to Wellington streets today to show their opposition, but Labour has become increasingly in favour of it.
Prime Minister Helen Clark yesterday said some bill opponents were "demanding the right to be able to thrash and beat children", and Dr Cullen said hysteria would pass once people understood the bill properly.
"We're not going to have thousands of mums and dads lined up in court because a hand happened to come into contact with a bottom."
The private member's bill returns to Parliament today and another drawn-out debate is expected.
National stalled the legislation's progress two weeks ago by taking up as many speaking slots as possible and lodging amendments. It plans similar tactics today.
"When 85 per cent of New Zealanders are opposed to this bill, we would be a pretty sick Opposition if we didn't do our best on their behalf," said shadow leader of the house Gerry Brownlee.
As a Government bill, the proposed law change would get priority, instead of being dealt with only once every two weeks as a private member's measure.
Labour wants to avoid the bill, which a majority of MPs are expected to support, making slow and headline-grabbing progress.
It has looked at several other options for fast-forwarding progress, including the unusual measure of taking urgency to push through a private member's bill sponsored by another party's MP.
But New Zealand First and United Future were split or opposed to the urgency proposal, which led to its being shelved.
The Maori Party, which supports Ms Bradford's bill, yesterday said it opposed the law change being pushed through hurriedly, which cast into doubt Dr Cullen's claims that Labour had the numbers to pass the urgency proposal.
"It was clear it was causing a degree of internal angst in New Zealand First in particular, and the ongoing relationship is more important than getting the numbers for the urgency motion," Dr Cullen said.
The bill removes from the Crimes Act the defence of justifiable "reasonable force" against assault on a child.
Supporters say smacking has been illegal for more than 100 years.
Opponents say removing the "reasonable force" clause from the Crimes Act will turn parents into criminals if they even lightly smack their children.
The war of words over the bill became increasingly heated yesterday as surveys showed a big majority against the legislation.
A One News/Colmar Brunton poll found 83 per cent of those surveyed believed in smacking children.
Bill opponents advertised in major newspapers yesterday and prepared for protest marches today.
Helen Clark retaliated by attacking "extreme-right-wing fundamentalist groups" that she said were some of the bill's most vocal critics.
"New Zealand has it on its conscience that our rate of child death and injury from violence, including in the home, is appalling," she said.
"It is a stain on our international reputation, and I cannot see how those who are demanding the right to be able to thrash and beat children can possibly then turn around and confess concern about what is happening to our children."
The PM dismissed opinion polls showing majority opposition to a ban on smacking as being based on false assumptions, with questions based on assertions that were wrong.
"It is a crime of assault now to touch anybody for any reason," she said. "Most such assaults are technical assaults on which the police would never dream of acting.
"The issue is how to empower police so that they can get a conviction where someone is clearly beating a child."