Children are the most vulnerable New Zealanders and there is no excuse for not properly investigating allegations of abuse against them, Police Minister Judith Collins says.

The Independent Police Complaints Authority yesterday announced it would investigate how police nationwide had dealt with child abuse cases.

The inquiry follows complaints made in June of delays in the police response to child abuse cases in the Wairarapa.

"The authority has established a dedicated team of investigators and lawyers focusing solely on this inquiry," authority chairwoman Justice Lowell Goddard said.

"The authority has received evidence that there have been delays or issues with management of child abuse cases in districts other than the Wairarapa and is therefore treating this as a nationwide inquiry."

Ms Collins today welcomed the widened inquiry and made a commitment to addressing any problems it found.

"It's one of the problems that I've inherited and I'm very pleased to see that at least something is done," she told Radio New Zealand.

"There is no excuse for our most vulnerable New Zealanders, children, not having these cases investigated properly and I'm very aware that when police deal with these cases, they are very concerned to make sure that they do their best."

Safer Homes in New Zealand executive director Jane Drumm was shocked the problems could be more widespread and said police did their best.

"... I know that family violence cases and, particularly child abuse cases, turn their stomachs," she told Radio New Zealand.

"They absolutely want to do their best for these little children and they want to sort the matter out."

But Liz Kinley, of child protection organisation Jigsaw, said there was a feeling police did not give child abuse cases the priority they deserved.

"Not only is evidence going cold and investigations become much more unlikely to reach a satisfactory outcome if the data is not collected promptly but also children are left exposed to people that have harmed them, often people in their family network, people they have to see regularly, who have not been called to account," she said.

The inquiry would focus on police conduct, practices, policies and procedures, in relation to child abuse cases.

It would consider the manner in which child abuse cases are received, prioritised and investigated by police, Justice Goddard said.

The authority would also conduct an independent audit of child abuse cases and investigate complaints about police handling of child abuse cases.

People with relevant information, such as police staff, social workers and staff of child welfare agencies, families and other members of the public, could make submissions, which would be received in confidence, Justice Goddard said.