Two senate crossbenchers facing potential political death at the next election will launch a High Court challenge to laws changing the way Australians vote for senators.
The legislation passed parliament after a marathon Senate sitting on Thursday and Friday and speculation is mounting that the move could pave the way for the federal government call a July double-dissolution election, clearing out both chambers.
Family First senator Bob Day is behind the legal challenge but Liberal Democrats senator David Leyonhjelm is also involved and others may jump on the bandwagon.
Senator Day said he believes the challenge has a 50-50 chance of success and insists he's doing the federal government a favour because it could head off a potential expensive election re-run.
"These laws will make it easier to get rid of pesky independents like me," he said.
He finished off the paperwork for the legal challenge on Saturday and will lodge the writ on Monday.
"We're confident others will see the value in what we are doing," Senator Day told AAP.
Independent senator Jacqui Lambie has ruled out joining the court action.
The basis for the challenge is that three million voters will be disenfranchised by the laws because their votes will no longer result in electing political candidates.
They are also in breach of the constitution, Senator Day says.
Senator Day is also seeking an injunction from the High Court to intervene before the election to decide whether the electoral changes are constitutionally valid.
Senator Leyonhjelm told AAP he believed there was an outside chance the challenge could be successful.
Special Minister of State Mathias Cormann dismissed the prospect of the legal action.
"We are very confident that the reforms passed by parliament are consistent with all the relevant requirements in the constitution," he said.
Opposition Leader Bill Shorten flagged that Labor would take a careful look at Senator Day's arguments and the legal basis of the challenge.
Labor opposes the changes, saying they will entrench the coalition's power in the upper house and keep independents and minor parties out.
It will end the situation where small parties can win a place in the Senate with only 0.5 per cent of the primary vote.
The changes allow voters to allocate their own preferences above the line on the Senate ballot paper.
And if they choose to vote below the line they won't have to number every box - in some states that could be up to 100.
A spokesman for Senator Ricky Muir said that he was not involved with the High Court challenge but would be following it with intense interest.
Senator Muir had many concerns with the rushed Senate election legislation, which is why he had unsuccessfully moved a number of amendments.
"Now that the government has finished taking its instructions from the Greens, maybe they can get back to the more important aspects of running the country - dealing with the things that matter," he said.
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