The government needs the votes of four of the six Senate crossbenchers to get its three-stage package through the upper house when parliament returns next week.

Labor backs stage one and wants to bring stage two forward but is not supporting the final stage.

The government has flatly rejected splitting up the package.

Centre Alliance, which controls two votes, has been negotiating with the government on measures to reduce gas prices to ensure the extra cash some Australians will get won't be chewed up by rising power bills.

Senator Rex Patrick said on Wednesday he anticipated a "package of solutions which include both long and short-term options".

Labor frontbencher Penny Wong says the minor party needs to lay bare any deal it strikes with the government over gas prices and be held accountable for it.

"If there's a deal which they've already done on the gas prices they should probably tell you what it is," she told reporters in Adelaide on Thursday.

"I hope South Australians will be holding Centre Alliance accountable for this supposed deal around gas prices and making sure three, six, nine months from now that Centre Alliance has actually delivered lower gas prices."

The senator said Senator Patrick and his Centre Alliance colleagues - Senator Stirling Griff and MP Rebekha Sharkie - have shown the government they will have an "easy ride" in the upper house this term.

That comes as the Senate is already more conservative, she stressed.

"It's quite clear Senator Patrick and Senator Griff and Ms Sharkie here from South Australia are prepared to throw in the towel even before we get to parliament."

The final stage of the coalition's plan will flatten the tax rate from 32.5 per cent to 30 per cent for people earning between $45,000 and $200,000 from mid-2024.

Finance Minister Mathias Cormann says this will "take the bracket-creep monkey off all Australian workers".

"We call on all parties in the parliament to demonstrate goodwill and facilitate speedy passage of that very important piece of reform legislation," he told reporters on the sidelines of the G20 summit in Japan.

Senator Cormann has not been able to confirm what measures are being discussed with Centre Alliance, saying the government doesn't provide a running commentary on every crossbencher's proposal.

It is expected the Senate will be asked to back a procedural motion next week which will clear the decks for a debate on the tax bill immediately after the lower house passes it, in a bid to get parliament's nod quickly.

So far the only crossbencher to back the coalition's full plan is Senator Cory Bernardi, a former Liberal.

One Nation, which holds two seats, has vowed not to support it, while Senator Jacqui Lambie hasn't declared her hand.

The Greens, who control nine votes, are opposed.

The first stage of the plan will mean extra cash for low and middle-income earners in coming months.

Labor will only support the second stage due to kick in from 2022/23 if the government brings it forward to the coming financial year.

This stage will top-up a low income tax offset and mean more people - earning up to $45,000 instead of $41,000 - will get a 19 per cent tax rate.

Australian Associated Press