The Greens MLA wants ACT petrol stations to be forced to display the full price for fuel per litre, not just the price for drivers with discount shopper dockets.

Mr Rattenbury's bill is set for debate in the Legislative Assembly next week but is likely to be defeated unless he can gain the support of opposition MLAs.

The government will not support the proposal because the matter is under review at a national level by the Ministerial Council on Consumer Affairs.

ACT Attorney-General Simon Corbell said the government would prefer to see a nationally consistent approach to price advertising.

But the system has already changed over the border after the NSW Coalition government ruled that petrol stations would have to display the real price for fuel and not the discounted price.

Mr Rattenbury has modelled his bill on the NSW legislation and he said on Wednesday that it made sense for the ACT's petrol price displays to be consistent with those over the border.

"The thing is these national processes can literally take years," he said.

"With this coming in, in NSW, clearly it is a scheme that is considered to work.

"This is a way of just giving consumers the right information."

Mr Rattenbury said retailers should be required to display the "actual, non-discounted price of the most popular fuels they sell" instead of advertising a cheaper price that would apply only for drivers who presented a discount voucher.

"We've had feedback from consumers who have been frustrated by this practice and they feel that it's unfair advertising and it lacks clarity," he said.

He said that a change to the rules could also assist the territory's small and independent supermarkets that did not use discount petrol vouchers as a means of drawing shoppers into their stores.

But Mr Corbell said it was the wrong time to be considering a change to petrol price advertising rules.

"First of all, we'd prefer to see a nationally consistent approach on what information is presented on billboards," he said.

"The matter is before the Ministerial Council on Consumer Affairs, on which I represent the ACT, and the council has not yet reached a definitive view on the issue.

"Now there's been a change of government it would be preferable to understand the Commonwealth's position on that."

Mr Corbell said that elements of Mr Rattenbury's bill could not be achieved in the ACT.

The bill would require the ACT to have inspectors who would go to petrol stations and verify the octane level of the fuels that were sold.

Mr Corbell said the ACT government did not have the capacity for such work.

"In NSW they do have that … but we have no capacity to do that in the ACT," he said.

Comment was sought from the Canberra Liberals but not supplied.