Australia's climate chief has warned a road user charge could discourage drivers from switching to an electric vehicle, as the federal government confirms no timeline has been set for the new tax.

State and federal Treasurers are working on a replacement to the fuel excise, which could be used to help pay for road maintenance and repair.

Chair of the Climate Change Authority Matt Kean, a supporter of the user-pays model, said it may be too early to impose a national charge while EV uptake is sluggish.

“In time, when there are more EVs on the roads, obviously they should pay their fair share as well,” he said.

Currently, about 10 per cent of new cars sold in Australia are electric.

Climate Change Authority modelling shows that to meet an emissions reduction target of 62-70 per cent on

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