Victoria Police and road safety groups have told a parliamentary inquiry they do not support introducing a one-metre rule for cars overtaking cyclists

The laws were proposed by Greens MP Samantha Dunn, and would require drivers to make sure there was a one-metre distance between their car and cyclists when they overtake.

The law would apply in 60-kilometre-an-hour zones; at faster speeds it would be 1.5 metres.

Victoria Police members gave evidence at a public hearing, saying they opposed the laws out of safety concerns.

Acting Senior Sergeant Ryan Burns told the hearing police were concerned they would lead to motorists crossing the centre line to give bicycles room.

"The results also suggested that drivers find it hard to accurately establish the lateral distances, and police noticed some drivers leaving larger distances, resulting in potential collisions with on-coming vehicles," he said.

Queensland officially adopted the laws in April following a two-year trial, following the lead of South Australia and New South Wales, who also introduced the rule earlier this year.

Not enough evidence for one-metre rule: TAC

VicRoads and the Transport Accident Commission (TAC) told the inquiry that although it already encouraged drivers to adhere to the one-metre rule, the agencies did not support making it law.

Representatives told the hearing there was not enough evidence that the laws worked, and it would be difficult to evaluate their effectiveness in Victoria without baseline testing.

Victoria Police said the law would be too subjective. ( 774 ABC Melbourne: Clare Rawlinson )

Samantha Cockfield from the TAC said they could also create more tension between cyclists and motorists.

"I think the biggest concern for us all is introducing a law where people can't always easily comply may bring about more tension in a system where there is a lot of tension already between motorists and cyclists," she said.

"It is a real issue, there is tension, and we're very aware of it as agencies.

"We're not suggesting we do nothing, we are suggesting that we continue and add weight to what we've been doing in terms of education."

Laws 'too hard for police to enforce'

Police also said the laws would be hard to enforce.

Acting Senior Sergeant Burns said the current laws required a safe distance, and it was up to officers to use their judgement.

He said switching from that requirement to a fixed distance was problematic.

"It's not possible to definitely determine if there was less than one-metre distance unless the distance was very small," Acting Senior Sergeant Burns said.

"The offending motorists often contest the violation based on a subjective judgement of the distance.

"So essentially it's hard for us to prosecute the one-metre rule effectively."

In other jurisdictions, police have used in-car video to issue infringements.

But the hearing was told there were only about 50 cars fitted with cameras in the Victoria Police fleet, and the majority were in regional Victoria.