There's growing speculation the Turnbull government is about to split its controversial $50 billion company tax cut plan so at least small business enjoys a benefit.

But Treasurer Scott Morrison wouldn't be drawn on talk the government would hive off the first tranche of its tax cuts - for businesses with turnovers under $10 million - to secure a pre-budget win.

Mr Morrison told reporters there has always been two parts to the package.

"There has been the longer term glide path for all companies down at 25 per cent and there's been a change to the definition of small business (from less than $2 million to less than $10 million turnover," he said on Wednesday.

The centrepiece of last year's budget is aimed at eventually lowering the company tax rate cut to 25 per cent through incremental cuts over the next 10 years.

The rate presently sits at 30 per cent, apart from small businesses with a turnover of less than $2 million which pay a rate of 28.5 per cent.

Labor MP Ed Husic said the opposition would likely support tax cuts for smaller companies, but couldn't resist laying the boot into the government.

"If they split this up today, the coalition is signalling that they've basically taken out of the top drawer the white surrender flag," he told reporters in Canberra.

But the devil would be in the detail of any amended legislation, he said.

"Having lived through so many coalition announcements that promised big and failed to deliver, we will check every 'i' is dotted and every 't' is crossed before we give a final signal," Mr Husic said.

A key crossbench senator has thrown her support behind carving up the proposed tax cuts to give smaller businesses a leg-up.

Tasmanian independent senator Jacqui Lambie says parliament should be "throwing everything" it possibly can to support small and medium-sized enterprises.

"If you really want these SMEs working, especially in these rural and regional areas where they're doing it tough, then give them a bigger tax cut and throw it at them now because they need it," she told ABC radio.

But Senator Lambie has no appetite for cutting taxes at the big end of town.

"I certainly think giving more tax cuts to big business - especially when there's 600 out of the top 1500 companies not paying tax and we're going to give them more tax exemptions - I'm not into that at all."

Independent senator Nick Xenophon expects the 27.5 per cent tax rate for companies with a $10 million turnover to be passed when it reaches the Senate, but is not so sure about dropping it to 25 per cent for all companies.