Her defection means the Nationals have lost four seats since Mr Barilaro has been leader;Lismore,Murray,Barwon and now Port Macquarie.

"The NSW Liberals and Nationals have delivered unprecedented investment across the Port Macquarie electorate and to put this in jeopardy and hold the Premier and the government to ransom during this COVID-19 pandemic was unnecessary,unhelpful and frankly politically reckless and unreasonable,"Ms Williams said.

"The events of the past week have represented a further example of a course of conduct and dealing that has once again effectively been condoned and failed to be addressed.

"My community deserves to be represented in Parliament by members and leaders that are focused on their needs and their aspirations and they rightly expect to have policy overshadowing politics".

Ms Williams'resignation comes as the Nationals try to repair relations with the Liberals and negotiate changes to the koala policy.

The four major changes the Nationals want include reducing the number of koala feed trees,which have been increased from 10 to 123,and redefining the definition of core koala habitat.

But ministers have been warned to step up after Better Regulation Minister Kevin Anderson told the Nationals party room that Mr Barilaro had done much of the"heavy lifting"with the policy.

One senior Nationals minister said all the party's ministers had to work to ensure they delivered the changes to the policy for regional NSW. The party room is also expecting changes to the policy.

Another Nationals MP,who spoke on the condition of anonymity,said he was confident the policy would be resolved and Mr Barilaro would"return,stronger than ever".

Mr Toole,the MP for Bathurst,will front a party room meeting on Tuesday ahead of another sitting week of Parliament.

He said COVID-19 and the drought had presented big challenges for the state but they were"not insurmountable".

"If you talk to anyone right now,they’re being faced with big decisions - it's not only government and we’re very conscious that the decisions we make have impacts for everyone,"Mr Toole said.

"There are so many businesses out there having to make tough decisions about how to structure their business and flex it to adapt to the times[and] there are farmers preparing for the biggest crop in years and trying to rebuild a balance sheet and stock numbers knocked around by drought.

"They need to be front of mind for us."

Ms Berejiklian said on Sunday she had made it known personally to Mr Barilaro that he would be given any support he needed during his leave.

"I have made sure he knows that,and I wish him and his family well during this time,she said.

"I think it is always appropriate for people to be upfront and honest about what they are going through and I commend that."

When asked if she was confident she could work with Mr Toole and find a resolution to the koala policy,Ms Berejiklian said:"I am a Premier who is very tolerant and patient and I get on with everybody."

One senior Liberal minister,who asked not to be named,said Mr Toole would be"easier to deal with than Barilaro"and the next month would be a trial run to see if Mr Toole was leadership material.

Several Liberal ministers,including Police Minister David Elliott and Transport Minister Andrew Constance,were highly critical of Mr Barilaro's threats.

Who is Paul Toole?

The deputy Nationals leader grew up on a farm outside Bathurst and was a regional school teacher until he was elected to Parliament in 2011.

One of nine children,Mr Toole advocated for better regional healthcare and transport when he first arrived on Macquarie Street.

The 50-year-old father of three was made Minister for Local Government in 2014 before being handed the racing and forestry portfolios in 2017.

After extending his margin in Bathurst to more than 17 per cent at the 2019 state election,Mr Toole was appointed deputy Nationals leader and Minister for Regional Transport and Roads.

He has maintained a relatively low profile since arriving at Parliament but was seen to struggle with the complexities of the controversial council amalgamations.

Despite this,he is viewed as the “safe option” to take over leadership from Mr Barilaro.

- With Tom Rabe