But the Liberals had a sudden change of heart, prompting chaotic scenes in the chamber on Thursday. Dumped cabinet minister Eric Abetz. Credit:Andrew Meares Conservatives Cory Bernardi and Eric Abetz, crossed the floor. Senator Abetz was a cabinet minister and leader of the government in the Senate until Prime Minister Malcolm Turnbull dumped him from the frontbench in the wake of the September leadership coup. The spectacle also saw the Nationals split from their senior Coalition partner to side with Labor and the Greens. One veteran senator said he had "never seen anything like it" before. Family First's Bob Day, Palmer United Party's Zhenya "Dio" Wang, Liberal Democrat David Leyonhjelm, independent John Madigan and Senator Bernardi originally proposed the Tertiary Student Services and Amenities Fees motion. Motions are largely symbolic and unlike legislation are not binding.

Senior cabinet minister Christopher Pyne assured Senator Leyonhjelm on Wednesday night that the government would support the motion, which said mandatory fees can be charged if agreed to in an annual mandatory ballot.​ Acting Opposition Leader Penny Wong. Credit:Andrew Meares But Liberal senator Scott Ryan said on Thursday the proposal did not go far enough and was no longer supported by the government. "This motion supports creating the illusion of voluntary student unionism through the use of campus or institution wide ballots, however compelling all students to join and fund an organisation by a ballot of their peers is just as illegitimate," Senator Ryan said. Senator Ryan, who has made voluntary student unionism a pet issue during his career, left the chamber to abstain rather than be seen voting against a motion on voluntary unionism.

Penny Wong, Labor's leader in the Senate, said the division "goes to the heart of the government". A few weeks ago Eric Abetz was the government's Senate leader, now he's split from his Liberal colleagues on the floor of the Senate "A few weeks ago Eric Abetz was the government's Senate leader, now he's split from his Liberal colleagues on the floor of the Senate," she said. "Except for his fellow insurgent, Cory Bernardi, the rest of the Liberal Party lacked the courage to vote." Senator Abetz said he was entitled to split from the government.

"There is a long tradition of Liberal senators having the ability to cross the floor on matters important to them. I exercised that right on a matter of principle for which I have fought for since first becoming a Liberal student." Senator Bernardi told Fairfax Media he crossed the floor because was supporting Liberal Party policy and the motion was a step in the right direction. "It's always been my position to support long-standing Liberal Party policy that accords with the philosophical principles or the Liberal party, that's what I did today," he said. Follow us on Twitter Follow Latika Bourke on Facebook