Ride-sharing service Uber began operating in defiance of the law and the West Australian Government did nothing to stop it, the WA Supreme Court has been told.

About 400 taxi plate owners have launched legal action against the State Government, claiming it should never have allowed Uber to operate.

Lawyer Martin Bennett, acting for the owners, said taxi owners and drivers were having to pay a series of costs associated with regulations while Uber drivers did not.

He said taxi plate owners and drivers had borrowed money to fund the purchase of plates, had complied with regulations, fitted cameras and paid insurance, yet Uber drivers did not.

Mr Bennett said there was no commitment to pursuing any new legal cases against Uber, and Premier Colin Barnett had suggested Uber was "here to stay".

He said the market was affected by "disorderly, defacto deregulation" and more prosecutions of Uber drivers should have proceeded.

Transport Services Manager Director Nina Lynne told the court 29 Uber drivers had been or were being prosecuted, and no more charges would be laid until those cases had been completed.

Government lawyer Craig Bydder told the court the call for greater prosecution was "contrary to authority".

Mr Bydder said there was a difference between not prosecuting and not taking action, and cases were ongoing.

Obligation to prosecute will be clarified: lawyer

Outside court, Mr Bennett said the case was not about compensation.

"Potentially it will clarify the government's obligations in relation to Uber, whether or not they're obliged to prosecute or whether there's a constructive policy of not prosecuting," Mr Bennett said.

"This isn't about compensation, it's about a level playing field and the government's attitude will be known at the end of a green paper followed by a white paper.

"That's all three to five years off, the industry needs to know the position before then."

One of the named applicants, Peter Martin, read from a statement outside court in which he accused the Government of corruption and incompetence.

"The Government is stealing our plates and without paying any compensation to us," he said.

"We abide by the rules of purchase, and operating our taxis, set by the Government, but it is supporting the overseas, illegal operations of these illegal ride sharers."

Justice Tottle has reserved his decision.