Cormann's poker face holding on tax cuts

Don't play poker with Mathias Cormann.

The finance minister is playing a high stakes game on two sets of tax cuts and he's already seen some opponents fold and others start to crack.

The June sitting of parliament is make-or-break for the coalition as it tries to get its corporate and personal income tax cuts made law.

Labor supports the first half of the personal tax cut plan because it helps lower- and middle-income earners, but says the second half is a handout to the rich.

Opposition Leader Bill Shorten has offered his own generous tax cuts over the next four years, but won't support the coalition's seven-year plan to radically change the tax brackets.

He wants the government to split the bill in half.

Sitting across the poker table, the inscrutable Cormann keeps raising the stakes.

"We will not split the package. Bill Shorten has to make a decision whether he wants to stand in the way of personal income tax relief for low- and middle-income earners," Cormann said during the week.

Either Labor votes for the full deal and everyone gets their tax cut, or Labor rejects it and Shorten is the Grinch Who Stole Christmas-In-July.

It appears the high stakes game is working.

Labor is reportedly considering voting for the full $140 billion tax cut and banking on winning the election to reverse the parts it doesn't like.

That is itself a risky game, even though the polls suggest Shorten will be in power after the next election.

Cormann doesn't have such a good hand in his other poker game.

Labor and the Greens don't support dropping the corporate tax rate from 30 per cent to 25 per cent for businesses with turnover above $50 million.

So Cormann is steadily working on the crossbenchers, picking them off one by one.

Tasmanian independent Steve Martin joined the Nationals on Monday, so he's on board with the tax cuts.

Senators David Leyonhjelm, Cory Bernardi and Fraser Anning also back them.

The two Centre Alliance senators at this point are a 'no', but are still weighing up their options, while independent Tim Storer doesn't support the cuts but will consider them as part of wider tax reform.

Pauline Hanson is key, but Cormann's negotiating has helped split One Nation.

Hanson was signed up to the tax cuts and she shook Cormann's hand on a deal, bringing Peter Georgiou and Brian Burston with her.

Then the Longman by-election was called and Labor realised they needed to win over One Nation voters who preferenced candidate Susan Lamb in 2016.

Shorten launched blistering attacks on Hanson and One Nation over the corporate handouts - and she folded.

Hanson backed out of her earlier deal, and the decision broke her party, with Burston going public on Thursday, promising to vote for the corporate tax cuts in defiance of his leader.

Hanson said her long-time supporter had sold himself out.

"For him to turn around and do this to me -- it's hard. But I'm going to keep going. And I'm going to get good people in that parliament beside me," she said.

Cormann's game got a bit trickier.

"Obviously from my point of view it would be preferable if all One Nation senators remained committed to the consensus that we reached," he told Sky News on Friday.

A split in One Nation doesn't help the coalition get the deal through, even if chaos in the party helps the coalition in the long run win back conservative voters.

Cormann will keep negotiating, but the senate-whisperer might have found his toughest opponent in Derryn Hinch.

The Victorian senator is playing the same tough poker game as Cormann, and he wants the cuts to be limited to companies with turnovers under $500 million.

Cormann is ruling that out.

But with two key sitting weeks before July 1, that high stakes game becomes tougher to play if Hinch is the last one standing and willing to go all in.