Conservative Christian groups say they will be forced to break the law if Parliament stops allowing the reasonable use of force to discipline children.

A string of churches, Christian schools and individual Christians told a parliamentary committee in Mangere yesterday that Green MP Sue Bradford's "anti-smacking" bill flouted their biblical beliefs and would "open the way for religious persecution and intolerance".

Pastor Peter Boyd of Manurewa's Covenant Presbyterian Church, part of a breakaway group that split from the Presbyterian Church in opposition to homosexuality, said Christians believed the Bible was the authority and they were bound to follow it.

"Christians in general are law-abiding people. They pay taxes even though they might not agree with what their taxes are spent on," he said.

"But when you have a case where the law of the Bible and the law of the land conflict, they are forced to obey the law of the Bible.

"In this case too sharp a line is being drawn. Christians in particular, and others too, will be forced to disobey the state to do what is right according to their conviction."

Of 55 submitters heard yesterday, 22 supported the bill. Kim Gosden of the Waitakere Abuse and Trauma Counselling Service said that almost all parents who came to counselling about violence had experienced violence in their own childhoods.

"They may have intentions that they do not want to parent the way they were parented, but they do. They do end up using weapons or something. They do end up hurting," she said.

She tabled an anonymous statement by a client who had wept as she told the story of how she and her five siblings were slapped and strapped by both their parents. She and three of her siblings had chosen not to hit their own children because "we all feared our mother in particular and did not want our kids to feel about us as we felt about our parents".

"I do not believe our parents would have changed their behaviour and attitudes voluntarily, but any legislative intervention would have at least alerted them to the values that were prevailing in society," the client said.

An Epsom teacher, Peter Luiten, said his father used to punish him by hitting him on the side of his head, once giving him injuries that put him in bed for three days.

When Mr Luiten himself started teaching, he hit his students in the same way until one boy's parents complained. He then stopped hitting his pupils.

He kept on hitting his two daughters until his marriage broke up. He married again and hit his two step-sons.

"It was only a court order that finally stopped me," he said.

"I never believed that what I was doing was right in the first place. I knew it was wrong. I just did it anyway.