The number could be up for criminals who hide behind the anonymity of prepaid cellphones.
Police are calling for all prepaid customers to be registered on a national database, to stop pay-and-go phones being used by criminals - who believe there is no way to trace the user and know the phones can be disposed of easily.
Phones are available over the counter in New Zealand without buyers having to identify themselves or give traceable credit card details.
Detective Senior Sergeant Darrin Thomson, from the Wellington metro crime unit, told The Dominion Post that prepaid cellphones provided a "significant challenge" for police investigating high-profile serious crimes and crime groups.
"The use of prepaid cellular phones is a common use amongst the criminal fraternity, particularly at the higher level, and anything that would help us thwart that anonymity would be fabulous."
Mr Thomson said adopting a system similar to Australia's - where all phone buyers would have to present a passport or other official form of identification at the point of purchase - would help catch criminals.
"We've got a point of contact straight away, which is a really, really good thing."
The call for change comes as officials in Britain plan to extend the powers of state surveillance by ensuring everyone who buys a mobile registers their identity on a national database.
Vodafone spokesman Paul Brislen said it would support a government-mandated industry-wide scheme to introduce a compulsory register of prepaid phones in New Zealand.
Vodafone has a customer base of more than two million accounts, of which about 70 per cent are prepaid.
Telecom has just over 2.1 million mobile customers, about 60 percent prepaid. Spokeswoman Rebecca Earl said the company was open to discussions about a register.
Mr Thomson said police were continually liaising with the Justice Ministry and telecommunications companies to enhance the ability to fight crime. Creating a register for prepaids would be "no different" to a White Pages or Yellow Pages service.
He envisaged the register would be available for telecommunications companies who have people misuse their product, or for police investigating crimes.
"I certainly don't think that this is a system to be implemented that would be abused - it's no different from you and I having a landline. People who are going about their lawful business, which is a great majority of the community, have got nothing to worry about."
A Privacy Commission spokeswoman said the commission would follow developments in Britain with interest, but questioned whether the "extensive collection of cellphone user information" would achieve the aims sought.
She said the commission would expect to be involved in early talks on any such proposal.
- The Dominion Post