Internal emails reveal that police bosses sought assurances in the wake of significant problems with burglary statistics in South Auckland - and were wrongly told that a national review had taken place showing that the system was overwhelmingly robust.
Police deny the assurances gave them a false sense of security over the integrity of burglary statistics.
Emails released under the Official Information Act also reveal that Police Commissioner Mike Bush was told about issues with crime statistics in South Auckland in November 2009, 2 years before police launched an internal investigation that lifted the lid on improper practices for recording burglaries.
The 2012 investigation found that about 700 burglaries had been wrongly recoded to other crimes or incidents in the southern region of Counties Manukau between July 2009 and April 2012.
Five officers were disciplined, while the report raised questions over pressures to meet crime reduction targets, and whether there were wider problems with statistics.
Police have said it was an isolated problem.
Police bosses, including then-deputy commissioner Mr Bush, were notified of the investigation by email in August 2012. "The recoding of burglary offences to non-burglary offence codes appears significant over those years and is believed to have led to a false report of a reduction in burglary offences," the email said.
Then Police Commissioner Peter Marshall immediately asked a number of follow-up questions, and he and Mr Bush were told in response that no other crime types were reviewed. They were also told that a national review had showed that recoding rates were "fairly consistent with each other, except one Wellington area shown to be higher than the average".
But the review only covered areas in Auckland, and no other areas - including Wellington - were looked at.
Mr Bush, who was in charge of Counties Manukau from 2008 until March 2011, told the Herald that responsibility for crime statistics lay with the area commander.
Counties Manukau Superintendent John Tims said the email author was mistaken, but denies that the incorrect information swelled the confidence of the police executive in the integrity of national crime statistics. He said there was no need for a national review because the Auckland one had not given any cause for wider concern.
The email trail also shows that there were concerns over burglary statistics in Manurewa as early as November 2009, when Mr Bush was district commander.
The email falls within the time period of the 2012 review, although it relates to an area of Counties Manukau that the review did not cover.
It was sent to a number of police, including Mr Bush.
"I have discussed the issue with the TCU [tactical crimes unit] sergeant ... who (to put it mildly) was outraged that his 'integrity was being brought into question'," the email said.
"Please be assured that there is no 'cooking of the books' going on at Manurewa."
Mr Tims said regular checks in 2009 had revealed "atypical patterns" in Manurewa, but further inquiries found "reasonable explanations".
Crime spike 'no surprise'
The number of crime incidents in Counties Manukau rose by more than five time the national average in the five years to 2013, while the number of "alarm sounding" incidents spiked 10 times faster than the national average.
But police say this is unsurprising given the hundreds of extra officers, a focus on prevention, and higher level of alarm users in the district.
An internal police report in 2012 showed that hundreds of burglaries were wrongly reclassified as incidents, which are not counted in official recorded crime statistics. From mid-2010, officers changed between 11 and 26 burglaries to incidents every month, many of them to "alarm sounding".
After the revelations, police said there were no issues with burglary statistics in any other police areas. But when the recoding rates for burglaries across all districts were asked for, police said they did not keep these numbers.
Police released the number of recorded incidents across each police district, which rose 6.6 per cent nationally from 2008/09 to 2012/13. In Counties Manukau the increase was 36.5 per cent.
Nationally the number of "alarm sounding" incidents rose by 9 per cent over the same period. In Counties Manukau they almost doubled from 861 in 2008/09 to 1655 in 2012/13 - a 92 per cent rise.
There were also sharp increases in Counties Manukau of "traffic incident" (up 68 per cent), "bail breach" (up 198 per cent), and "attempted suicide" (up 221 per cent).
Counties Manukau Superintendent John Tims said the increase in incidents was due to a focus on prevention, as well as the increase in officers from 754 in November 2008 to 1068 by the end of 2010. He said no investigation was needed.