The ALP has refused to rule out blocking a plebiscite on gay marriage and launched a strident personal attack on the Prime Minister over the issue, flagging a potentially acrimonious start to Australia’s 45th parliament.

On Sunday, Opposition Leader Bill Shorten told reporters a same-sex marriage plebiscite was the “second best option”, a stance that could foreshadow a bitter political fight about the vote.

Despite recent calls for a more bipartisan approach to politics, it may also offer a glimpse into the character of the next parliament, due to sit for the first time on Tuesday.

“We want to have marriage equality and we want to do it as quickly as possible,” Mr Shorten said.

“A vote in the parliament is the quickest, cheapest, least divisive mechanism.”

Mr Shorten said he was “worried Malcolm Turnbull will just stuff it [plebiscite] up”.

“He stuffed up the republic referendum, he stuffed up the NBN and he stuffed up Senate reforms when he promised to fix it,” Mr Shorten said.

“Malcolm Turnbull doesn’t even support a plebiscite. He’s only doing it because he is too weak to stand up to the radicals in his own party.”

Ireland overwhelmingly voted to legalise same-sex marriage in 2015. Photo: Getty

The PM, however, says a plebiscite is the quickest way to legalise same-sex marriage and doubts Labor’s commitment to blocking it.

“I think Labor will support it,” he said.

Frontbencher Christopher Pyne lashed the ALP for “basically thumbing their nose at gay couples having the same status as different sex couples”.

Combative parliament looming?

The spat presages the first sitting days of Australia’s next parliament, which has a list of potentially divisive matters to consider: same-sex marriage, differences on superannuation changes, the explosive refugee debate, Labor’s push for a banking royal commission and the Coalition’s desire for tougher union policing. Combined, they create a picture of partisan dispute.

Malcolm Turnbull’s first term as an elected PM won’t be easy. Photo: Getty

When Mr Turnbull replaced Mr Abbott as PM in mid-2015 he promised politics would be less aggressive and more consultative, even across party divides.

But since the hung parliament of 2010, Australia has been governed by a combative, often nasty legislature.

It reached boiling point during Labor’s Gillard government when then-opposition leader Mr Abbott doggedly attacked his adversary.

The policy difficulties worsened when Mr Abbott won the 2013 election and was met with a divided Senate.

Given Mr Turnbull’s double-dissolution election delivered five crossbench MPs in the lower house and 20 in the Senate, securing the safe passage for legislation could be the biggest challenge facing Mr Turnbull.

The enemy within

Mr Turnbull will need to keep his eyes on Coalition enemies too. Tony Abbott is another major sub plot in the new parliament.

An intervention last Friday foreshadowed the likely tone of his contributions and the heartburn they could cause the PM.

Mr Abbott might make things tough for Mr Turnbull. Photo: ABC

Mr Abbott said the government had been in office since 2013 “but not in power” on the issue of budget repair.

He also said the Coalition would not succeed if it tried to govern from the sensible centre.

“Our challenge is not to move closer to Labor in the hope of being a smaller target,” he said, suggesting it should adhere more strictly to its conservative principles.

Speaking to ABC TV on Sunday, Mr Turnbull refuted the claims. He argued that his government was already fighting on principle, citing the union-fighting bills it used for calling the double dissolution election.

The Abbott dynamic will be a distraction for the PM who will need to tiptoe around the senate, go toe-to-toe with the ALP in the lower house and try to score enough points with substantive policy work to support his pitch for re-election in 2019.

If he survives that long.