Family First senator Bob Day will be taking the Government's new Senate voting laws to the High Court next week.

Key points: Senator Day to lodge legal challenge against senate voting legislation

Senator Day to lodge legal challenge against senate voting legislation Says three million votes may 'exhaust or die' as a result

Says three million votes may 'exhaust or die' as a result Liberal Democrats will support the legal challenge

The legislation, which will make it harder for micro parties to get elected, passed both houses yesterday.

The Coalition bill passed with the support of the Greens and independent Senator Nick Xenophon after a marathon sitting session of more than 28 hours.

Prime Minister Malcolm Turnbull described its passage as good for democracy, but Senator Day said he would lodge a legal challenge against the legislation on Monday.

Under the new laws, voters who issue a limited number of preferences at the polling booth will have their ballot discarded if their preferred candidates are excluded from the race.

Senator Day told the ABC that he would argue on the potential disenfranchisement of voters, following the High Court's response to missing ballot papers from Western Australia in the last federal election.

"Just 1,200 votes went missing and the High Court was sufficiently concerned about that to order a rerun because of the way it would impact the outcome of the election," he said.

"What their attitude might be to 3 million votes exhausting or dying deliberately as a result of these laws is the question that needs to be asked."

On Twitter, Senator David Leyonhjelm said the Liberal Democrats would help to fund the High Court challenge.

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Monash University's Nick Economou said exhausted votes would become an issue at federal elections if voters continued to vote one above the ticket of their choice.

Dr Economou warned voters had been voting above the line "at rates of about 90 per cent or more" since the system was introduced in the 1980s, and if that pattern continued, up to 20 per cent of votes could be exhausted.

Veteran psephologist Malcolm Mackerras said he was confident of a speedy High Court challenge.

He told the ABC that he would do everything he could "to help that challenge so that the High Court can strike this thing down as being unconstitutional".

"The words 'directly chosen by the people' appearing in Section 7 and in Section 24 [of the constitution], in my opinion, commands that the electoral systems must be candidate-based," he said.

"Now, what this thing does is to introduce a party list system. What I cannot stomach is the idea of the Liberal Party suddenly deciding to abandon the democratic values of the Australian constitution and suddenly deciding to embrace Greens principles, purely because it will help them to engineer the double dissolution they want and to get rid of the crossbench senators whom they dislike."

However, Special Minister of State Mathias Cormann said the Government was very confident the reforms were consistent with all the requirements of the constitution.

"The whole purpose of the reforms is to empower voters to directly determine where their preferences go and hence who they ultimately end up helping to elect to the Senate," he said in a statement.

"Under our system the voter has control of what he or she wants to do with their vote all the way through and who they help elect to the Senate. In our opinion that is as it should be."