Government MPs have been told airing their opposition to possible changes to tax breaks for property investors could harm the coalition's re-election chances.
Placing an annual cap - said to be about $20,000 - on what investors can claim against their taxable income for negatively geared properties is being considered as part of the government's tax review package.
Liberal backbencher Cory Bernardi is among a group of coalition MPs warning the government it would be "political suicide" to change existing rules.
But Deputy Prime Minister Barnaby Joyce has urged them to "cool their rockets", saying the government is going through budget planning in a methodical way.
"Obviously people have to clearly understand that we have an election coming up and you don't want to ventilate in such a way as the fruits of your endeavours are that you end up in the opposition benches," he told reporters in Sydney on Friday.
"I know there is a sense of a febrile nature out there at the moment and everybody expects we will, every second of the day, announce every iteration of every section of planning towards the tax policy, but we're not going to do that."
Senator Bernardi said it would be "mad" to mess with negative gearing, like the Labor Party has done.
"I don't think we should have a bar of it quite frankly," he told ABC radio.
The federal opposition wants to limit negative gearing to newly constructed properties and cut the capital gains tax discount to 25 per cent from 50 per cent.
Liberal MP Ewen Jones believes there is some scope for changes, pointing out some investors were negatively gearing more than 20 properties.
"Is that what we envisaged when we brought in negative gearing?" he said.
The backbencher wants Treasurer Scott Morrison to be given the breathing space to develop a good policy.
Shadow treasurer Chris Bowen said Liberal backbenchers were now setting the government's economic policy.
"There is a leadership vacuum in this government and the lack of leadership from Malcolm Turnbull and Scott Morrison is being filled by these backbenchers," he told reporters in Sydney on Friday.
