Deputy Prime Minister Barnaby Joyce has defended colleagues' right to vote against laws after a coalition MP warned he'd cross the floor on the government's "bad" superannuation policy.
Queensland Nationals MP George Christensen is demanding changes to the proposed $500,000 non-concessional lifetime cap and its "retrospectivity", along with the $1.6 million pension fund transfer balance cap.
"It's not a threat - I am going to cross the floor," he told ABC Radio on Wednesday.
"That's because it's bad policy."
Mr Joyce, the Nationals leader, said it was Mr Christensen's right to cross the floor but it wouldn't win him any plaudits.
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"Obviously it doesn't come with any recommendation, or laurels or promotion," he told Sky News on Wednesday.
The deputy prime minister defended the policy, saying it was taken to an election and would help balance the budget.
Treasurer Scott Morrison said any MPs seeking to change policies taken to the election would have to find alternative savings.
"If something comes off the table then something else has to come on the table."
Mr Christensen said the changes outlined in the May budget and taken to the election were "Labor-style policies" which hurt people who've worked hard all of their life.
He described it as a "lazy government" measure which had cost the coalition Senate seats.
If the coalition ends up with 76 seats in the lower house, Mr Christensen's opposition could threaten the super changes.
Independent MP Bob Katter is also vowing to oppose it "tenaciously".
Mr Christensen is also promoting a new group, Queensland Conservatives.
Labor's superannuation spokesman Jim Chalmers said Mr Christensen's position - which echoed that of other members including Tasmanian Liberal senator Eric Abetz - showed there was a "civil war" within the government.
"Before the election, Mr Turnbull said he was proud of these changes and that they were iron clad," Mr Chalmers said.
"Now he doesn't even know how many of his own MPs will vote against his policy."
Labor has called for an independent expert review of the changes to consider their retrospectivity, how they interact with each other and what effect they will have on confidence in the superannuation system.
Mr Turnbull said on Monday he understood some MPs were not happy with the policy, but promised consultation on "transitional and implementation issues".
Mr Morrison said calculating the cap from budget night instead of 2007 would come at "significant cost to the budget".
He said the next step would be preparing draft legislation and ensuring all MPs had a "better understanding of the specifics".
