Police will end its policy giving officers discretion to only warn drivers with breath test readings over the prescribed limit of 22mg but less than 27mg of alcohol per 100ml of breath, from September 21.

From this date all drivers exceeding 22mg, but under 37mg/100ml, can opt to replace their breath test readings with results from blood or urine analysis, which will be used as evidence in court.

Drivers will continue to be charged for readings of 37mg or more.