The Police Association has welcomed today's compromise on the bill changing the law around smacking.

Prime Minister Helen Clark and National leader John Key this morning announced they had agreed to an amendment to Green MP Sue Bradford's Crimes (Substituted Section 59) Amendment Bill.

The agreement means the bill is now almost certain to be passed in two weeks' time.

The bill removes a defence of reasonable force and opponents said it would criminalise parents who smacked their children.

Today's amendment would make it clear police had the discretion not to prosecute complaints against a parent where the offence was considered "so inconsequential" there was no public interest in it going ahead.

Police Association President Greg O'Connor said the new clause upheld police discretion.

"Parliament is to be congratulated on coming to this sensible position," he said.

Previously the Police Association expressed concern that police would have to prosecute even minor offences under the law -- some supporters of the bill said that was incorrect.

Helen Clark said she believed the public would swing behind the anti-smacking bill following the compromise.

She said the common ground established was a result of Parliament's "senior players" getting involved towards the end of the debate.

She felt the compromise would be supported by the majority of New Zealanders.

However, some polls have suggested up to 80 per cent of the public oppose the bill and a poll currently running on nzherald.co.nz suggests today's compromise will not be enough to persuade the majority - 59 per cent of those who voted saying the change did not make it a good law.

There were reports that many of an estimated crowd of more than 2,000 mainly fundamentalist Christians who opposed the original bill and converged on Parliament this afternoon seemed unaware of the last-minute amendment.

But Destiny Church leader Bishop Brian Tamaki said the move was a huge backdown by the Labour Government.

Deal

At an extraordinary press conference this morning, the Prime Minister set out how the deal was reached and said there was now cross-party support.

The compromise sees wording inserted into the bill guiding the police not to prosecute all parents who smack their children.

Miss Clark said the change has the support of both the bill's sponsor Sue Bradford and Mr Key.

She said: "Sue Bradford has always been clear, as I have been, as John Key has been, that there is no desire to see decent, good parents marched into court for something that is inconsequential."

Miss Clark said she began looking for a resolution to the impasse last week and worked with Parliament's legal experts looking at police prosecution guidelines.

On Sunday she went to Ms Bradford, who said she was willing to look at it. She then went to Mr Key at question time yesterday and met with him last night before reaching agreement on the final wording.

Both Labour and National will support the amendment and the final reading of the bill - now expected on May 16. This will assure Ms Bradford of an overwhelming majority.

Mr Key said the change achieved National's three key aims.

They were to give comfort to parents they would not be prosecuted for lightly smacking their kids; to give police clear guidance they should not pursue "inconsequential" matters and at the same time send a strong anti-violence message to New Zealanders.

At present, the bill would make it unlawful to use any form of physical discipline on a child for the purposes of correction.

The compromise is being introduced by United Future leader Peter Dunne.

To date Labour supported the bill and all but one of National's MPs have opposed it.

Ms Bradford welcomed the compromise. She said: "I don't think we needed this amendment at all in terms of what the bill was seeking to achieve but we needed it to reassure New Zealand parents and to achieve the kind of political consensus across Parliament."

What the new amendment says:

To avoid doubt it is affirmed that police have the discretion not to prosecute complaints against a parent of a child, or person in the place of a parent of a child, in relation to an offence involving the use of force against a child where the offence is considered to be so inconsequential that there is no public interest in proceeding with a prosecution.

The bill comes back to Parliament today. Ms Bradford previously had 63 votes behind the bill, enough to have it passed into law. A majority in Parliament is 61.

Yesterday the Maori Party, which holds four votes and the balance of power on the bill, confirmed it was not going to change its stance and said it would continue to support it.

The bill removes from the Crimes Act the statutory defence that allows "reasonable force" to be used to correct children.

The bill removes from the Crimes Act the statutory defence that allows "reasonable force" to be used to correct children.

Opponents said that meant even the lightest smack would be a criminal offence.

Supporters say smacking has been illegal for more than 100 years and the defence is allowing people to get away with savagely beating children.

It has divided Parliament and there have been bitter debates.

An amendment proposed by National MP Chester Borrows which would allow light smacking was expected to be voted on today. Unless some MPs change their minds, it was set to be defeated.