"It is not a practice found to be performed at supervised drug and alcohol bus testing sites."
The fake breath tests (PBTs) were first reported to Victoria Police late last year. Once aware of the claims, five years of data, 1500 devices and more than 17.7 million tests were analysed.
"Disappointingly, 258,463 PBTs or 1.5 per cent of all tests had been falsified,"
Professional Standards Command Assistant Commissioner Russell Barrett said.
"This conduct will not be tolerated, any member found engaging in this practice from today has been put on notice they will be investigated.
"I had not heard of our members engaging in such a practice, we let ourselves down, we've let the community down. It stops now."
Victoria Police are now appointing an external investigator to determine "the root causes of the behaviour", "underlying cultural and behavioural issues" and "supervision and management practices that resulted in the behaviour continuing to go unchecked".
"The question we all asked was 'why?' There could be a number of reasons but the main rationale I believe is to hide or highlight productivity," Barrett said.
"Whatever reason our workforce may come up with, it isn't acceptable.
"There is no evidence to suggest fraud or any criminality. Similarly, there is nothing to suggest that any of this activity has impacted on any prosecutions."
Police are hoping to lean on technical advice about how to future-proof testing devices.
"We are considering the feasibility of regular audits, the ability for the PBT to include the detail of the operator and quality assurance measures."