Women's Refuge and the association representing New Zealand psychotherapists have joined the chorus of concern about the appointment of Christine Rankin to the Families Commission.

They say Ms Rankin's opposition to the child smacking law makes her unsuitable for a post where she would advocate on behalf of children.

Labour's social development spokeswoman Annette King this morning released letters the groups had written to Prime Minister John Key and Social Development Minister Paula Bennett, querying Ms Rankin's suitability for the commission.

Ms Rankin was appointed by Ms Bennett as one of seven commissioners last week and the Government has so far stood by its decision.

"John Key and Paula Bennett need to listen to the growing number of community and expert voices calling for the Government to reverse its decision and do the right thing," Ms King said.

The National Collective of Independent Women's Refuges said it was concerned Ms Rankin's appointment may prove detrimental to the well-being of New Zealand families and undo the work of the commission.

Commissioners should have proven experience in commitment to the purposes of the commission, said chief executive Heather Henare.

"They need to support the existing child discipline law, which protects children from assault on the same basis as adults."

Ms Rankin spoke out against the repeal of Section 59 of the Crimes Act, which removed the defence of reasonable force for parents who physically punish their children.

"Ms Rankin's suitability for a position representing and advocating on behalf of children is surely questionable when she clearly does not support legal measures to protect them from assault," Ms Henare said.

Ms Rankin's appointment had the potential to undermine the credibility of the commission, she said.

Marlyn Robson, secretary of the New Zealand Association of Pyschotherapists, also expressed concern about Ms Rankin's stance on the child discipline law.

"I am not sure of the suitability of someone with her very public private and public life to be a role model, and wonder what exactly she has done to reduce child abuse."

Sunday newspapers reported Ms Rankin was involved in the break-up of the marriage between Wellington real estate agent Margo McAuley and Kim MacIntyre.

Ms McAuley was found dead in October last year. Her death has been referred to the coroner.

Mr MacIntyre and Ms Rankin married in January this year.

Ms Rankin has strongly denied having an affair with Mr MacIntyre before Ms McAuley's death.

Her appointment to the Families Commission caused an uproar even before the reports were published because of her high-spending track record when she was head of Work and Income.

Earlier a member of the Families Commission's Whanau Reference Group, Druis Barrett, resigned in protest at Ms Rankin's appointment.

United Future MP Peter Dunne, who set up the Families Commission in 2002, has also been scathing of the appointment.

- NZPA