Victoria Police faked hundreds of thousands of breath tests because of a “meaningless” target, a review finds.

An investigation into the widespread faking of roadside breath tests by Victoria Police officers has found that police went against their own road safety strategy by forcing negative readings.

Over 258,000 breath tests were falsified by officers to return negative readings, according to a review last year.

It found officers had blocked the straw entry hole of breath testing equipment with their finger, or blown into the straw themselves, to create negative readings.

The investigation, run by former chief commissioner Neil Comrie, found the “root cause” of the practice was a target requiring 99.5 per cent of all preliminary breath tests (PBTs) should find drivers to be under the legal alcohol limit.

“[The target] creates the perverse situation that proactive drink-driving law enforcement that achieves more than 0.5 per cent positive PBT tests annually is regarded as not meeting the required budget performance outcome for PBTs,” the report said.

The target - which came from the Victoria Police budget - was labelled “meaningless and unachievable” by many officers, with “no reasonable or scientific basis”, the report says.

But still, police were teaching new recruits to fake the tests, seemingly without questioning the purpose.

“It has been a common experience for new recruits to be inducted into the practice early in their careers through instruction from more experienced members,” the report said.

Officers also reported being “instructed to avoid detecting impaired drivers”.

The investigation warned that similar incentives could be affecting the integrity of drug testing, and that the problem is probably not limited to Victoria.

The report made 23 recommendations - including mandatory ethics training for all officers every two years - all of which have been accepted by Victoria Police.