Chalmers and Frydenberg have more in common than they like to admit

Jim Chalmers and Josh Frydenberg have more in common than they like to admit.

The two former (and perhaps future) rivals are both sharp media performers. Both are highly energetic and ambitious. Both have also had complicated relationships with their respective prime ministers.

And this week both have been reminded of the difficulty of pursuing policy reform.

In the case of Frydenberg, it was the mere suggestion of revisiting the GST as part of broader reform to make the tax system more efficient.

"We need a considered but ambitious national debate about lifting the GST and removing some exemptions, with a significant portion of that additional revenue to fund a major reduction in income tax," he wrote in his memoir, A Grateful Son.

It's hardly an original or radical idea, having been floated over the years by everyone from the Liberal luminaries who brought the GST to life, John Howard and Peter Costello, to corporate leaders such as Matt Comyn and David Thodey, and economists Richard Holden and Saul Eslake.

But Frydenberg's attempt to revive the debate was shot down instantly by Angus Taylor.

"We will not be raising the GST in the middle of a cost-of-living crisis," the opposition leader told Insiders. "We won't be raising taxes," he declared more broadly, which suggests the Coalition will instead seek to fund its growing list of expensive promises through spending cuts alone.

Not that Frydenberg is deterred. His book, and various media interviews this week weighing a potential political comeback, have received a mixed response among Liberal MPs in a party room that has shifted to the right since he was last there.

But the former treasurer is upbeat about the broader public reception. If anything, he's even more energised. And after planting the flag on the GST, Frydenberg isn't walking away from his argument about the need to tackle difficult reform.

Chalmers's difficult week

As for Jim Chalmers, reminders have been coming thick and fast, ever since the May budget, of how bruising reform can be.

After months of blowback over negative gearing and capital gains tax changes that weren't taken to an election, now it's trusts.

Labor is confident it will ultimately win the support of the Greens to impose a 30 per cent minimum tax on discretionary trusts, but fears this could be an even tougher fight than the earlier tax battles, particularly when small business is already angry over a separate matter — the Tax Office decision to ban credit card payments.

The week became even more difficult for Chalmers after the prime minister appeared to suggest he'd been sidelined.

After trying to settle the nerves of anxious Labor backbenchers in Tuesday's caucus meeting, the prime minister then appeared on stage at an Australian Chamber of Commerce and Industry (ACCI) dinner to claim credit for fixing the Tax Office problem.

"Andrew did text me last Thursday morning," Albanese said, referring to ACCI chief executive Andrew McKellar. "By Friday morning we had an announcement."

The comment not only created the impression Chalmers had been overruled, but it also suggested government positions could be quickly influenced by an industry group text message.

Chalmers, clearly, couldn't let that sit.

He then revealed he had in fact spoken to the prime minister a day earlier. "On the Wednesday I had discussions with the PM. We agreed it would be appropriate to find a better way through."

In other words, it was a joint decision taken between the two of them before the text message from Andrew McKellar.

Labor MPs divided on 'rift'

By Question Time yesterday, the prime minister was denying any rift, describing the decision as unanimous.

Tension between a prime minister and treasurer is nothing unusual, as Josh Frydenberg can attest. When it's publicly on show, that's a problem.

The opposition made the most of it, stirring both the prime minister and treasurer in parliament. Labor MPs, meanwhile, were divided.

Some reckon Chalmers should have seen the Tax Office troubles coming earlier. Others reckon it was a bit rich for Albanese to pass the buck after over-egging the benefits of removing credit card surcharges with a social media post suggesting "your morning coffee could be cheaper".

Either way, it's in the interests of neither to appear at odds.

Ultimately, Albanese and Chalmers agree on the big stuff. They both know the government is facing challenges. Both are confident Labor will be in a stronger position this time next year. And both agree sticking with the budget tax changes is the only course.

But delivering reform is proving more difficult by the day.

Late yesterday, the Coalition and Greens joined forces in the Senate to deliver a blow to the government on another front. They've sent Labor back to the drawing board on its plan to remove the more generous private health insurance rebate for over-65s.

That's another $3 billion savings measure up in the air.

As both Chalmers and Frydenberg would surely agree, there's no easy path to repairing the budget.

David Speers is national political lead and host of Insiders, which airs on ABC TV at 9am on Sunday or on iview.