Key Points:

One of the great ironies of the anti-smacking debate is Sue Bradford's touching faith in the police and the justice system - and even more ironic given her former life as a protester and champion of the powerless, during which she certainly clashed with police on occasions.

I have two perspectives on the debate. As a mother of pre-schoolers I have my personal views, which have changed since I had children.

But whether I choose to smack or not to smack - or whether anyone does - isn't the issue. I know that as a middle-class woman in a happy marriage my chances of being prosecuted for smacking are practically nil.

I have another perspective. As a criminal lawyer who has both prosecuted and defended people charged with assaulting a child I think the repeal of section 59 of the Crimes Act will have disastrous and unnecessary consequences for a small group of people.

The people who will eventually suffer from the repeal of section 59 are the most vulnerable and powerless members of our community - and their children.

I say the repeal of section 59 is unnecessary because in my experience it is just that - unnecessary. I never lost a case which I prosecuted on the basis of section 59.

I drafted an indictment against a man who was convicted of smacking his 4-year-old son about five times on the backside with an open hand, leaving marks.

I think the jury convicted because the man smacked his boy too hard and because the boy was smacked not for a deliberate misdemeanour but because he soiled himself.

I prosecuted a man, a loving father, for using a belt on his mildly intellectually handicapped and very challenging teenage daughter after she damaged her bedroom.The jury were hugely sympathetic to the father but when I asked them in closing if they would not have intervened to stop the man had they been in the room at the time I knew they would find him guilty.

I saw the realisation dawn in their eyes. Not one of them would have stood by and let that happen "as a father's right", so they could not say it was reasonable discipline.

I've had far fewer cases as a defence lawyer, but I've never fancied my chances of going to a jury and saying: "Look, bashing that child with a jug cord was perfectly reasonable."

Of course there will be the occasional case where section 59 has excused parents who overstepped the mark, but these are not cases where a child has been thrashed or beaten or injured. I challenge anyone to find a case where section 59 has excused a real bashing that left a child injured.

In my experience of those sorts of cases, the section 59 defence simply isn't used. The accused denies the assault. New Zealand juries are not stupid.

Sue Bradford doesn't trust the New Zealand public so I find it amazing that she has so much faith in both the police and the justice system.

She is proposing to give a huge amount of discretion to individual police officers.

She expects them to wisely ignore the letter of the law. They won't. I know this and so does National MP Chester Borrows, with whom I worked and who was a superb, wise and compassionate detective sergeant.

The police may not, and I'm sure will not, prosecute every case of smacking, but they will be obliged to at least investigate - and therein is the harm. Picture this: a child at the centre of a custody battle comes back from an access visit. Mum questions the child: Did Daddy smack you? Has Daddy ever smacked you? The child says yes.

Mum takes the child to the police station. She is vocal and upset. "Investigate" sounds benign. It is not.

That child will be put through the evidential interview process. It's not a process you want your child involved in. Dad will be asked to go to the police station to make a statement.

All this will probably be good for lawyers. Probably no charges will be laid, but the child and the family will have been through a traumatic and damaging experience.

This scenario will happen without a doubt. It will happen over and over again and the children at the centre of Sue Bradford's concern will suffer it. The poor and powerless will be far more vulnerable.

Most police are honest and upstanding and we are lucky to have them.

Some are not. Some get caught up in a "means to an end" approach to criminal law. Some will use this legislation - and the discretion it gives them - for the wrong purpose.

It won't be me or people like me who suffer this. It will be the very people Sue Bradford has fought for in so many other ways.

The Government should forget party politics on this one. We are lucky to have an experienced former police officer, who also has a law degree, sitting in the House. He is saying, for many different reasons, don't give the police this much discretion. He's right, and we should listen to him.

* Michele Wilkinson-Smith is a lawyer