The mother of a man killed by a drunk driver says the police investigation into why officers failed to stop the vehicle is a "cover-up".
Paul Cowper, who was 21, and two other young adults were killed, and two people seriously injured, when Raymond John Hansen crashed into their van in Taranaki in 2005.
Hansen had been seen driving dangerously prior to the crash. Officers who had briefly pursued him set up surveillance but did not see him leave a bar and drive off.
The Independent Police Conduct Authority (IPCA) said Hansen was solely responsible for the crash but the officers could have prevented it.
Paul Cowper's mother, Angela Chamberlain, told Summer Report disciplinary action should have been taken against the officers.
"The police should have stopped (the crash) and I believe they are just as much responsible," she said.
"They are trained officers so they should have had a decent plan intact".
Ms Chamberlain says she is taking advice about legal action.
Central district commander Superintendent Russell Gibson says lessons have been learned from the failure to stop the driver, but the officers involved will not be disciplined.
"At the end of the day they made a mistake, they have learned with it ... they are very, very upset and distressed regarding this crash."
Mr Gibson told Summer Report police have made changes, so that in a similar situation officers would not wait in the hope of apprehending a driver as they were about to drive off.
"In such a such a situation again, we would take steps to either immobilise that vehicle, or impound it."
Officers could have prevented crash - IPCA
In mid-2005, Hansen crashed his stationwagon into a van which was carrying the five people at Normanby Bridge on State Highway 3.
The IPCA report concludes that Hansen was solely responsible for the crash.
However, it also says officers had briefly pursued his vehicle 30 minutes beforehand after seeing him driving dangerously.
The officers then found the vehicle parked at a Hawera bar and watched it with the help of CCTV cameras, but Hansen drove away undetected, and with fatal consequences.
The report says the officers could have prevented this by immobilising Hansen's vehicle or having it towed and they should have gone into the bar to find and arrest him.
Hansen was sentenced to nine years' jail in November 2005 after admitting several charges, including three of manslaughter.