Federal Labor has launched an extraordinary broadside against its longest-serving state government, with a senior Senator claiming Jay Weatherill has declared “open warfare” against the people of South Australia over his advocacy of a debate on increasing the GST.

Weatherill has publicly favoured a reform that would bolster Commonwealth coffers by raising the consumption tax to 15%, in exchange for the states being given a greater share of income tax revenues to offset cuts in health and education.

That’s put him at loggerheads with the national ALP, with Bill Shorten’s opposition staunchly opposing any GST increase. Last week, SA federal backbencher Nick Champion called on the party’s national executive to effectively muzzle Weatherill from pushing any proposal at odds with federal Labor policy.

But yesterday, the party’s deputy Senate leader, Victorian Stephen Conroy, stepped up the attack several notches, arguing Weatherill “is breaking his word to the people of South Australia”.

“I think Jay Weatherill is declaring open warfare on the people of SA,” he told ABC 891.

“In the lead-up to your last 2014 election, which he won by a very narrow margin as a minority government … he said, ‘We will never stand for a GST to be extended to food, health or education services or the rate be increased’. So the key message here is that Jay Weatherill is breaking his word to the people of SA.”

A Newspoll in yesterday’s Australian showed a majority of total respondents opposed a GST hike, with 54% against raising the rate to 15%, compared to 37% in favour and 9% uncommitted. Federal Labor is claiming the poll as vindication for its campaign, despite the fact the Turnbull government is yet to even adopt such a policy, and the poll also showed a majority of Coalition voters (51%) were in favour of it doing so.

Conroy said voters around the country were “sending a very loud and clear message … and the people of South Australia are no different”.

“They will be very perplexed about why their Premier, who promised that he would never support an increase in the rate of the GST, is now supporting it,” he said.

“If he wants to line up with [NSW Liberal Premier Mike] Baird, and he wants to line up with Malcolm Turnbull, to impose something that will hurt families and households, well, Bill Shorten is not going to stand by and support that.”

In a separate interview on ABC, Conroy dared Weatherill to call an early poll and test his support on the issue — despite the fact the state’s fixed electoral terms are mandated in law.

“If he is so convinced that this is the right solution, he is so convinced that increasing the GST is what he wants to fight an election on down the track, that he wants to be the father of the GST, well then he should go to the South Australian people,” Conroy said.

“They would reject utterly Mr Weatherill if he was to campaign on increasing the GST.”

Weatherill told Triple M radio the GST was “not a great tax, but what I’m for is to have an honest discussion about the problem”.

“We’re not raising enough money to pay for our health and education systems … there’s not enough money coming in to pay for what needs to go out,” he said.

“It’s a horrible thing to say but we have to raise some more cash somewhere … Now Mike Baird has proposed an increase in the GST, [and] I’ve said I’m prepared to look at that.”

Baird yesterday launched a GST offensive, arguing the tax rate should be raised to 15% by July next year to pay for health and education spending.

He believes $32 billion could be raised in 2017-18 to deliver the states $7 billion to cover funding gaps, with his “modified consensus plan” including compensation for low-income families and reductions to company and income taxes.

“I think that is a good deal,” he said in a video message posted on Twitter.

Baird said he was surprised by the Newspoll results, telling ABC radio: “I find that a remarkable number, to be honest.”

“A number of people aren’t aware of the acute budget challenges we have, particularly in the long term,” he said.

But Shorten said it was clear a 15% GST was “wrong, wrong, wrong”.

“Today we see more and more evidence that Australians aren’t buying the snake oil of Mr Turnbull and his Liberals,” he told reporters in Melbourne.

Shorten revealed yesterday he phoned Weatherill — after the Premier last week chided his Gonski funding commitment as lacking “coherence” — and “explained to him that Labor, unusually for an opposition, has fully funded its proposals”.

“We would have a tobacco excise increase and we would also make sure that we made multinationals pay their fair share of taxation,” he said.

“We would clamp down on the excessive and unsustainable superannuation tax concessions and we would stop wasteful government funding.”

Finance Minister Mathias Cormann said the commonwealth was talking to all the states and territories about tax reform ahead of a Council of Australian Governments meeting in late March.

“There’s still a way to go,” he told reporters in Canberra, saying the package would be revealed “in good time” before the election, likely in the third quarter of the year.

But Treasurer Scott Morrison intimated he was up for a fight on the GST.

“I’m no stranger to causes that don’t enjoy popular support,” the former immigration minister said.

“For five years, I campaigned heavily on what were very unpopular measures.”

— With AAP

*This article was originally published at InDaily