The State Opposition says a Labor government would immediately scrap a new taxi charge.

Swan Taxis says it will give customers the option of paying an extra seven-dollars-50 charge for bookings 24 hours in advance to ensure they are on time.

If the taxi is five minutes late the fee is waived.

The Labor leader Mark McGowan says it is a rort.

"If elected to office in two months, one of my first steps will be to remove this impost," he said.

"This taxi impost which is unnecessary, is counter productive and it will create disputation between taxi drivers and customers.

"It's the wrong thing to do and we will get rid of it."

Yesterday, the Transport Minister Troy Buswell defended his decision to allow Swan Taxis to charge the fee.

Mr Buswell says it was up to customers if they wanted to pay more.

"I view this as a service provider offering an alternate project to the public," he said.

"If the customers think it is a good idea and represents value for money they will use it, but it is a service offering that Swan Taxis is trialing in the market and we will see how it goes."

But the chairman of the Taxi Council Kevin Foley believes the public will not object to paying the fee if it means they can be guaranteed a taxi.

"I mean, it is a request from the community that a huge amount of people have said look I don't mind being charged a little extra if I can be assured I can get a cab," he said.

"The $9 fee is to contribute towards the driver coming off the road prior to that job being due to make sure that those people get a cab on time, particularly with important bookings of hook ups with other transport such as airlines.

"I haven't had a complaint in the last two years about any over charges but I've been inundated with complaints about not being able to get a cab on time.

"This is a trial and we're trying it out to see how it works, and I think to have this option is a great innovation.

"Certain drivers had to sign agreements to agree to do this.

"We did not allow just any driver to do it."