The Coalition, with the support of the Greens and senator Nick Xenophon, intend to give voters the option to allocate six or more preferences above the line to limit the influence of hidden party preference deals. Greens leader Richard Di Natale has committed his party to the Senate changes. Credit:Andrew Meares There were 110 candidates on the 2013 Senate ballot in NSW, for example, and anyone choosing to vote below was required to number all boxes. In 2013, 97 per cent of voters opted to vote above the line. The implementation of changes could clear the way for a snap double dissolution election, with angry Labor senators claiming on Wednesday that the Coalition and Greens were engaged in "cartel behaviour" to close the door to Parliament for all but the established Senate parties and Senator Xenophon. Voting reforms have strained tensions inside the Labor Party, with Opposition Leader Bill Shorten on Wednesday standing down Gary Gray as the party's spokesman on electoral matters. Mr Gray took a swipe at his own party last week, saying it was "sad" that the ALP was not backing the changes.

He will be replaced as shadow special minister of state by Brendan O'Connor and will ensure Mr Gray does not speak to the electoral bill when it returns to the House of Representatives with amendments. Glenn Druery at the Senate voting reform committee. Credit:Andrew Meares The introduction of optional preferential voting below the line addresses the concerns of ABC election expert Antony Green and constitutional expert George Williams. During a truncated hearing on Tuesday, Mr Green and other experts warned of a potential High Court challenge due to the anomaly in the government's electoral amendment bill that would deem six preferences cast above the line as a valid vote but the same preferences cast below the line as an invalid. Lee Rhiannon is in open conflict with former party leader Bob Brown Credit:Andrew Meares

The advisory report of the Joint Standing Committee on Electoral Matters - which was written in less than 24 hours after the completion of the short public hearing - green-lighted the government's intention to push ahead with abolishing the group voting ticket - the mechanism that has allowed minor parties to transform a tiny primary vote into a seat in Parliament through preference swaps. "A candidate with a strong policy position who is well known in their community has every chance of being elected. However, a candidate who wishes to be elected on preference deals that 'game' the system will no longer have this opportunity. The committee believes that this is in line with community expectations," the committee report stated. The committee rejected criticisms of veteran psephologist Malcolm Mackerras that the ballot does not properly reflect the constitutional requirement that the people select senators in a candidate-based system. Some believe the practice of party groupings on the ballot contravenes the Constitution. "The committee is aware of concerns that the bill does not end the influence of parties in the Senate voting system. Specifically, it has been noted that the order that candidates appear is effectively a form of preference harvesting with a subtle form of preference harvesting within parties still allowed. The committee does not accept this view and did not accept this view in its earlier discussion on this issue," it said. The committee also recommended that an initial first-preference vote count happen on election night to give an early reading of Senate results.

The electoral amendment bill was being debated on Wednesday as the government pushes towards a vote in the current sitting fortnight. In a fiery dissenting report, ALP senators said the bill was a "perverse response" to concerns raised after the 2013 election. "This bill will have the effect of maximising the number of senators elected representing major parties, such as the Liberal Party, and established minor parties such as the Greens political party. This will deprive independents and so-called 'micro parties' of votes and prevent new entrants from achieving election to the Senate, thereby entrenching the dominance of existing parties. If the Liberals and the Greens engaged in this conduct in trade or commerce they could be prosecuted for cartel behaviour," Labor said. The ALP also took exception to the speed at which the government has moved on senate reform, calling for a slow-down in the process until a bipartisan solution can be reached. "Parliamentary scrutiny in relation to this bill has been a farce. The bill has been rammed through this committee with less than half a day of public hearings and without the opportunity for all interested parties to make submissions or appear to give evidence," Labor said.

"The bill was passed through the House of Representatives before the committee had even reported. This demonstrates the inquiry was nothing more than a sham designed to cloak the bill in a veneer of respectability." Ricky Muir's dissenting report stretches to 34 pages. Follow us on Twitter