Liberal Democrat David Leyonhjelm is warning the government it will have to deal with at least seven "very cranky" crossbenchers if they push ahead with Senate voting reform.
The government wants to change the rules so voters choose their own upper house preferences, making it harder for very small parties to do deals and be elected on small primary votes.
The Senate houses eight crossbench senators, including Motoring Enthusiast Ricky Muir who was elected on less than one per cent of the vote.
Independent Nick Xenophon would likely be the only crossbencher to survive the changes due to his popularity in South Australia.
In response to the proposal, Senator Leyonhjelm has threatened to vote against government legislation to reinstate the building industry watchdog, despite supporting it in the past.
He doesn't think there's time for a double dissolution election, which would force all senators - including the backbench - to re-run.
"If they do that without a double dissolution then there'll be seven of us sitting on the crossbench in the next parliament and we'll be very cranky," Senator Leyonhjelm told Sky News on Sunday.
He believes the Turnbull government is failing to win over the crossbench, criticising the negotiating style of many ministers despite the change in leader from Tony Abbott.
That's why he believes the building watchdog legislation will fail for a second time and expects the numbers to go backwards from the last vote.
He says Prime Minister Malcolm Turnbull should be on the front line of talks with the crossbench.
"He is their best salesman," Senator Leyonhjelm said.
"Now if the key issue is crossbench support, and not some international conference or whatever, then their best salesman ought to be on the case."
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