SYDNEY — Australia's Liberal-National Coalition, the country's main opposition, has split after a row over hate speech laws, casting the future of Liberal leader Sussan Ley into doubt.

The center-right coalition split on Thursday for the second time in less than a year after the junior partner National Party severed ties with the Liberal Party, citing the Liberals' decision to back the government's hate speech laws.

Australia's parliament this week passed the Labor government's new anti-hate laws in the wake of the Bondi Beach mass shooting last month, with backing from the Liberals. Three National senators voted against the bill, saying it was rushed through parliament and could undermine freedom of speech.

In a show of solidarity, all National members quit the opposition's shadow cabinet late on Wednesday after three of their senators had earlier resigned for breaching coalition rules by voting against the Liberals' position.

"Our party room has made it clear that we cannot be part of a shadow ministry under Sussan Ley," National Party leader David Littleproud told reporters.

He did not rule out a return to the Coalition, refusing to "speculate", but said it was "probably a good thing" if Australia's two main conservative parties spent "some time apart".

Ley, whose leadership is under pressure, is yet to comment on the split. She released a statement on Thursday to mark the national day of mourning, saying "my responsibility as leader of the opposition and leader of the Liberal party is to Australians in mourning".

Though both parties in the Coalition voted against legislation tightening gun controls, the Liberals had sided with the Labor government on Tuesday to pass hate speech reforms introduced after the Bondi Beach attack.

But their Nationals colleagues abstained from the vote in the lower house and voted against the measure in the senate, despite a shadow cabinet agreement, citing concerns that the legislation had been rushed and posed a threat to free speech.

The laws includes provisions that will ban groups deemed to spread hate and introduce tougher penalties for preachers who advocate violence.

On Wednesday three Nationals frontbenchers offered their resignations, which Ley accepted despite a warning from Littleproud that if she accepted them the rest of the Nationals front bench would follow. The rest of the shadow cabinet duly resigned.

"This process was wasn't all Sussan Ley's fault," Littleproud said. "Prime Minister Anthony Albanese put her in this process. But it has been mismanaged by Sussan Ley."

Ley had already been struggling to assert her authority over the Coalition after being elected the Liberal party's first female leader after last year's bruising election defeat.

Some political analysts and observers had predicted she would be ousted by the end of last year and Thursday's events have reignited those conversations.

The Coalition, in its current form, dates back to the 1940s, and before the brief break-up last year, had not parted way since 1987.

The Nationals mainly represent regional communities and often lean more conservative than the Liberals.

Former Liberal Prime Minister Malcolm Turnbull, himself no stranger to scuffles with the Nationals, told the ABC both Coalition party leaders had "mismanaged" the disagreement and now faced an un-electability crisis.

Another former Liberal leader and one of the nation's longest serving prime ministers, John Howard, told The Australian Ley had had "no choice" after the Nationals senators' revolt and had "behaved absolutely correctly". — Agencies