If Labor is trying to mount a scare campaign about the GST, it hasn't spooked Malcolm Turnbull.
Labor used all bar one of its questions during parliamentary question time to quiz government benches on the impact of an increase in the GST, in what the prime minister described as the "beginning of not an especially scary campaign".
Mr Turnbull reminded the house more than once at the start of a four-day sitting week that the government had not proposed increasing the GST.
What the government is doing is consulting with social welfare groups, unions and the business sector on a new tax system.
He will also take up the issue with state and territory leaders at COAG in December.
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"We have not taken things off the table in some sort of panic response to feeble scare campaigns," Mr Turnbull told parliament on Monday.
In the Senate, Finance Minister Mathias Cormann also questioned NATSEM modelling released last week that showed low and middle income earners would be worse off if the GST increased to 15 per cent from 10 per cent or its base broadened to fresh food, health and education.
Senator Cormann said it ignored welfare payments being automatically increased for price increases.
Mr Turnbull also said it would be "inconceivable" that if there were any changes to the GST they would be made without compensation.
But Labor frontbencher Jim Chalmers doubts it will be enough.
"If anyone thinks that low and middle income earners ... will be adequately compensated by this government after they jack up the GST has got rocks in their head," he told Sky News.
Treasurer Scott Morrison said so far only the states, some retired premiers and the odd backbencher had talked about changing the GST.
He reiterated the government was not trying to raise more revenue to balance the budget.
"It's about trying to grow the economy and to lift the burden off people that have an income tax system which is punishing them," he told Sydney's 2GB radio.
Liberal backbencher Angus Taylor said the discussion had got to be wider than "a lazy GST tax hike", while his colleague Dan Tehan wants the government to consider applying GST to financial services, an idea previously raised by South Australian Labor Premier Jay Weatherill.
Removing the existing exemption would generate at least $18 billion over the next four years, helping offset a reduction in the company tax rate.
But Labor senator Doug Cameron said a decrease in company tax would just give "fat cat executives" salary increases.
Liberal Democrats senator David Leyonhjelm sees merit in broadening the GST to cover fresh food, saying there is no justification for it to apply to frozen vegetables but not fresh vegetables.
"Nutritionally there's no difference," he said.
