Koala bill caused a NSW Government crisis as John Barilaro says Nationals would effectively leave the Coalition.

In the explosive development Mr Barilaro threatened that all Nationals MPs would move to the cross bench.

But he confirmed Nationals ministers would not surrender their portfolios.

Mr Barilaro said he had not spoken to Premier Gladys Berejiklian before announcing his decision and she has summoned him to a meeting this afternoon.

The Coalition agreement has been under pressure after Nationals MPs expressed anger over proposed planning regulations that would give farmers responsibility for managing koalas on their properties.

Mr Barilaro said his MPs had been liaising with Liberal colleagues about the policy since late last year and that if the Nationals did not take a stand, they "would become the laughing stock of regional and rural NSW".

He said Nationals MPs were "all concerned about where, after six months of hard work, putting forward in my mind sensible amendments to the SEPP [State Environmental Planning Policy], that we felt that we were now being betrayed".

Mr Barilaro said the NSW Nationals would no longer:

* Support Government bills

* Attend joint partyroom meetings

* Attend Parliamentary leadership meetings

He said that would not change until the party's position on the koala SEPP is "considered", but also said the Nationals' seven ministers would not surrender their portfolios.

"I know there are Liberal members who would love to see that," Mr Barilaro said.

"They would love to see me resign today, see members resign today but that would be giving in."

He said his MPs reserved the right to support Government legislation if it affected regional areas.

'We are not anti-koala'

Under the new regulations, more trees are classed as koala habitat which will restrict land clearing.

Mr Barilaro said the Nationals would on Tuesday introduce a repeal bill for the current SEPP.

"The National Party stands for a thriving koala population," he said.

"We actually want to see the population double. We are not anti-koala.

"We think a SEPP like this is somehow a way to sanitise the regions, attack the property rights of landholders and do absolutely nothing to support koalas."

The Nationals have 13 Lower House MPs, while the Liberals have 35 and Labor 36.

In the Upper House, the Nationals have six, the Liberals have 11 and Labor has 14.

Yesterday, amid escalating tensions within Coalition ranks, Liberal MP Catherine Cusack described Mr Barilaro's behaviour as "bullying".

"The whole strategy is 100 per cent bullying," she said.

She said the koala SEPP had been updated "at the behest of stakeholders that came from their own electorates" after an "exhaustive" process.

"I think it's fair to say Liberal members … are really stunned and bewildered by this extraordinary behaviour by the leader of the National Party, who's also the Deputy Premier who we support in Parliament to deliver stability and loyalty to the Premier, the Cabinet and the Government," she said.

Both houses of the NSW Parliament are due to resume sitting next week.

The Deputy Premier said the next two sitting weeks would be tough for the Liberal Party, and said the Government's agenda would be derailed.

"But we need to flex a muscle and that's what we're doing today," he said.