Treasurer Scott Morrison says changes to the GST distribution formula would ensure the "egregious" situation that sees Western Australia receive back just 30 per cent of the GST revenue it pays is not repeated.

But the changes, which would establish a floor beneath which the proportion of GST distributed to each state could not fall, are "prospective" and would not be implemented until "once the system returns to normal".

Western Australia has been complaining for years about its falling share of GST revenue and lobbying Canberra for changes to the policy of horizontal fiscal equalisation, which sees GST revenue returned to different states at different rates so that the standard of services such as hospitals and schools are comparable for all Australians regardless of where they live.

For many years WA was a beneficiary of the policy but as a result of the mining boom in the state – which has now come off the boil – the west's share of GST revenue fell.