Car tax or project delays: Barnett

Colin Barnett says a proposed $100-a-year car registration slug will not go ahead if it proves too unpopular with the public.

But voters would wait longer for road projects to be built if was rejected, the Premier said.

He said the $2 billion airport rail link would proceed on the timeline announced but if the registration increase was abandoned, "it might mean some other transport projects are delayed". He was not specific about what those projects might be.

"No one likes a new tax, particularly one that is so widespread," Mr Barnett said. "Relative to the cost of operating a car, which is probably over $5000 a year, it is a bit less than a tank of petrol.

"So in that sense, it's relatively modest.

"But, nevertheless, if there is widespread opposition to that, it probably won't happen, which means that some transport projects will happen later rather than sooner."