Police have stopped chasing motorists who leave petrol stations without paying because of the huge numbers of complaints from retailers and a loophole that makes it hard to prove an intent to steal.
The estimated annual cost of fuel drive-offs in WA is up to $6 million, says the Motor Trade Association of WA.
Under current law, drive-offs are considered a "breach of contract", not a criminal offence, because buying fuel becomes a contract when the operator turns on the pump.
Motorists can be charged with stealing only if police can prove they intended to steal the fuel.
Association chief executive Stephen Moir said police struggled to prosecute drive-offs because motorists would simply claim they forgot to pay.
He said police evidently lacked resources to chase up the problem and the law needed changing to make stealing fuel a crime.
"The fundamental problem in WA is not the police, it is the legislation and how the Act is actually written," Mr Moir said.
The police pursued those drivers but most simply said they forgot and went back to pay.
"Our contention is that people don't forget," he said. "We have the same people reoffending."
A police spokeswoman said an agreement was reached with the association that "fill up and drive off" scenarios would be a civil matter and police would not take reports of them.
She said police would only investigate "reliable and credible" evidence of criminality or when actions inferred a motorist never intended to pay for fuel.
She said it was recommended that service stations implemented pre-paid systems.
Australasian Association of Convenience Stores chief executive Jeff Rogut said police needed to reinforce petrol theft as a crime and show a stronger commitment to catching offenders.
He said officers should contact identified offenders and charge those who did not go back to pay.
Mr Rogut said the onus on addressing the crime was too often shifted on to the industry and retailers would be disadvantaged if forced to install pre-pay systems.
He said petrol theft was a serious crime with significant financial losses and safety concerns for employees and the public.
Mr Moir said the association was working with police on techniques to deter fuel thieves, including wide CCTV networks.
Police Minister Liza Harvey said she was looking into ways to deal with the issue.