A government bill cracking down on bad driving is unreasonable and gives too much power to the police, Attorney-General Chris Finlayson says.
The government's Land Transport Amendment Bill will make alcohol interlocks mandatory for serious and repeat drink drivers, and will increase the penalties for drivers who flee the police.
Alcohol interlocks are devices which prevent a car from starting if the driver has been drinking.
However, Mr Finlayson said the bill also gave police the power to seize the vehicle of someone who had refused to identify a driver who had fled - if the police suspected that person knew the driver's identity.
Mr Finlayson said people who failed to provide information were not a road safety risk and impounding their vehicle would be disproportionate and unreasonable.
"The threshold for impoundment of a vehicle is lower for a person who has failed or refused to provide information than for a person who has committed an offence directly linked to road safety," Mr Finlayson wrote.
"I consider the power to impound a vehicle for 28 days in relation to a refusal or failure to provide information is not rationally connected to the primary purpose of ensuring road safety."
Mr Finlayson said the bill was inconsistent with the right to be secure against unreasonable search and seizure affirmed in the Bill of Rights Act.