New Zealand's stretched police force investigates less than 5 per cent of fraud cases referred from the banking sector, documents reveal.

Growing "traditional" demand in areas such as family violence has put pressure on police and meant emerging threats such as cyber-crime have at times gone un-policed.

Responding to rising crime rates and public concern about crime such as burglary, in February the Government announced a $503 million package to boost police officer numbers by 880 over four years.

Documents related to that policy were requested by the Herald under the Official Information Act and have now been published.

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They include a draft Cabinet committee paper prepared for former Police Minister Judith Collins in August last year - which makes very clear why a boost in police numbers was badly needed.

The paper, which was not presented, outlined a 55 per cent rise in family violence incidents attended by police since 2009, a 51 per cent increase in mental health incidents over that period, a 13 per cent jump in burglaries, and a significant increase in methamphetamine seizures.

In addition to those "traditional" areas of policing, new areas of demand were emerging, the paper noted, including:

• Anti-money laundering and fraud. "Police currently investigates less than 5 per cent of fraud cases referred from banking sector".

• National security and counter-terrorism. These are resource intensive and "mean that officers are reprioritised directly from organised crime work".

• Cyber-crime and online offending. This is a "rapidly growing area of unmet demand", and police currently has "only a limited capacity to respond to this category of crime".

The Herald reported this month that New Zealand no longer has a presence at a major Interpol facility fighting cybercrime because of a lack of funding.

The Cabinet committee paper notes that demand is not felt evenly across the country's 12 police districts, and a police model will, over time, reallocate staff to where demand - not simply population - dictates.

New Zealand's 2015 population per sworn officer ratio of 517 compares poorly to other jurisdictions such as Victoria, Australia (401) and Scotland (306).

"Unlike New Zealand with one police agency, most of these jurisdictions have other agencies undertaking policing activities such as national intelligence, cyber-crime and counter terrorism, for example the Australian Federal Police," the paper states.

"That resource is not accounted for in these ratios, and would increase the gap between New Zealand and comparable jurisdictions' police to population ratios."

In another paper presented to a Cabinet committee in December last year, Collins presented a range of options including one to recruit 1165 additional sworn staff and 295 non-sworn staff over four years, at a cost of $555 million.

In the final Cabinet paper presented by new Police Minister Paula Bennett in January an increase of 880 sworn officers and 245 non-sworn staff was proposed, at an extra cost of $503 million over four years.

That investment was announced by Bennett and Prime Minister Bill English the following month, along with new performance targets including improving response times for emergency call outs and have police attend 98 per cent of all home burglaries.