The Government is being told to rethink its planned register for child sex offenders.

LISTEN: Anthea Simcock of Child Matters speaks to Larry Williams about the sex offenders register

That's been the advice of the New Zealand Law Society at parliamentary hearings on legislation allowing the creation of such a registers.

Law Society representative Tim Stephens said one of the issues with the Bill is that it deals with child sex offenders as a whole, and isn't targeted at the subset that have high re-offending rates and are the particular problem.

"The proposed register that's in this bill ought to be redesigned, so that it's targeted at child sex offenders, who are likely to reoffend, rather than being automatically driven towards particular offence types."

An organisation that treats sex offenders is unhappy with the current proposal.

WellStop chief executive, and clinical psychologist, Lesley Ayland, said the register shouldn't be funded out of existing social service or police budgets, taking money away from effective actions against sexual abuse.

She also suggested the register should "never put people under 18 on it, please offer people incentives to get off it, such as reduced time with treatment upon completion, and please never make it public."

Meanwhile a National Party Members' Bill designed to crack down on child sex offenders has fallen foul of Bill of Rights requirements.

MP Jian Yiang's Bill would prevent offenders formally changing their names, a move to prevent them hiding their past.

However the Attorney General's ruled this would limit a person's right to freedom of expression and can't be justified under the Bill of Rights.