The Morrison government is closer to finding out whether it has convinced minor party Centre Alliance to back its full $158 billion tax plan.

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.

That is assuming Labor maintains its position of only supporting parts of a plan, in a form the government has rejected.

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

Senator Rex Patrick says negotiations are just days away from ending.

“The devil is always in the detail and we are still working through the detail,” he told AAP on Wednesday.

“We anticipate a package of solutions which include both long and short-term options.”

Finance Minister Mathias Cormann was not able to confirm what measures are being discussed.

“Consistent with our usual practice, we will not provide a running commentary on every proposal or suggestion that is publicly promoted by individual non-government Senators,” he told AAP in a statement.

Liberal Senator Jane Hume is confident the package will get across the line.

“I think everyone wants to see the little guy win here,” she told ABC TV.

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

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

The Greens, who control nine votes, are opposed to it.

The opposition backs the first stage of the plan, which will mean extra cash for low- and middle-income earners when they file their tax returns in the coming months.

But Labor will only support the second stage that is due to kick in from 2022/23, if the government brings it forward to the coming financial year to give the economy an extra boost.

The second 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

Labor also wants the government to defer legislation on the third stage, which 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.

The government has ruled out splitting the package.