Ms Pavey said it was sad to lose a great champion of the bush and she felt inspired to continue his work.

"To John, the carpenters in Cooma were more important than the ministers on Macquarie Street," she said in a statement.

"A strong National party is integral to a strong coalition and I am encouraged by the support my colleagues have shown me."

MPs Paul Toole and Adam Marshall are also considered contenders to lead the party and become the new deputy premier.

Mr Toole said he would deliberate on "how best I can serve our party" over the next 24 hours before announcing his final decision.

Mr Barilaro, who holds the seat of Monaro, said NSW would be best served by someone who had the passion and fight to forge on.

"I just don't have the energy anymore," he told reporters on Monday.

While the move comes days after Premier Gladys Berejiklian said she was leaving, the outgoing leader of the junior coalition party said he had been "thinking about this for a while".

Once mooted as a possible candidate for the federal seat of Eden-Monaro, Mr Barilaro on Monday ruled that out.

"I'm looking for a new career. I turn 50 in November, maybe a bit of a midlife crisis, but definitely thinking about what happens next. I will take some time out, but I genuinely won't be running for federal politics," he said.

Opposition Leader Chris Minns said Mr Barilaro would better serve the community from the back bench while the health crisis continued.

"I think it is putting personal ambition and a next career move first," he said.

Mr Minns said costly by-elections were inappropriate given 173,000 jobs were lost last month in the state and western Sydney businesses suffered a 70 per cent decline in turnover.

Treasurer Dominic Perrottet, who intends to run for the position of Liberal leader and premier at a party meeting on Tuesday, said Mr Barilaro would be missed.

"I know it is a decision John has been considering for some time, and I understand and support him in his decision," Mr Perrottet said in a statement.

"John is one of the fiercest and most effective advocates for the people of regional NSW that our state has ever known."

Mr Barilaro also said the strain of his ongoing defamation case against Jordan Shanks-Markovina, known as entertainer friendlyjordies, "played a big part of this".

"I don't know how many of you can endure what I've endured online," he said.

Mr Barilaro acknowledged the government would soon likely be headed by Mr Perrottet, who has emerged as the frontrunner over the weekend.

As NSW gets ready to open up from COVID-19 restrictions using the roadmap Mr Barilaro helped create, he said Mr Perrottet had the ability to lead the state into recovery.

"I'm confident that this state now has bright days ahead of us," Mr Barilaro said.

He would not be drawn on who the next Nationals leader would be.

Mr Barilaro has called a Nationals party room meeting for Wednesday, when he will formally resign and call for a ballot for a new leader.

Once that is settled, Mr Barilaro will work with the Speaker and the Electoral Commission to determine a date for a by-election in his seat.

Mr Barilaro said he was deeply grateful to the NSW Nationals and grassroots members.

"People are sometimes quick to write off the National party, but it's the Nats in government who are, and always will be, the praetorian guard of common sense," he said.

Australian Associated Press