Nationals MPs met for half an hour in Parliament House on Thursday morning to elect Mr Grant, a former police inspector who is the member for Dubbo.

Education Minister Adrian Piccoli remains deputy leader of the Nationals.

In a statement, Mr Grant said that to be elected Nationals leader was an "extraordinary honour".

He said he felt "humbled" by the decision of his colleagues and would "work my backside off" in the role.

Mr Grant, a relatively inexperienced politician who was elected to the NSW Parliament only in 2011, said he held dear the principles of "honesty, integrity and hard work" and intended to pursue those in the job.

THURSDAY, 9.15AM:

Former policeman Troy Grant has been anointed Deputy Premier of NSW.

Mr Grant, 44, who has been a minister for six months, was on Thursday elected unopposed by his Nationals colleagues a leader of the party, Nationals Whip John Williams said.

EARLIER:

Hospitality minister Troy Grant is favourite to become the next deputy premier of NSW and leader of the Nationals after education minister Adrian Piccoli announced he would not nominate.

In a statement, Mr Piccoli said he would support Mr Grant "who will make a great leader of the NSW Nationals."

"I look forward to continuing as Deputy Leader of the NSW Nationals and Minister for Education," he said.

Nationals MPs will gather on Thursday morning to elect a new leader after Andrew Stoner announced his retirement at the 2015 election.

Mr Stoner said his "difficult" decision to retire followed a request from his wife Cathy, who is dealing with serious "health issues".

He will step down as Nationals leader on Thursday morning but will remain in cabinet overseeing his portfolios, which include trade and investment, tourism and major events, until the election next year.

The member for the mid-north coast seat of Oxley, Mr Stoner has served in the NSW Parliament since 1999 and as Nationals leader since 2003.

He said the decision to retire from Parliament was made after a recent break with his wife and three children.

"I became aware of the seriousness of the issues with which my wife has been dealing," he said.

"She asked me to bring forward my plans for retirement and I didn't hesitate."

Mr Stoner his wife has been dealing with "some health issues and other issues".

He pointed out that last year the job meant he spent 250 days away from home.

"This has coincided with some very difficult family issues that have been faced by my wife and three children back at home," he said.

"I can no longer expect or ask my wife, Cathy, to face these issues alone".

Mr Stoner said he has "no job lined up, I'm not under any cloud. This is about putting my family first".

He said he could not see himself taking on full-time employment upon leaving politics but would consider part-time work.

Premier Mike Baird said Mr Stoner had been "a great leader of the NSW Nationals, a fine Deputy Premier and above all a passionate advocate for regional NSW".

Nationals state chairman Bede Bourke said Mr Stoner had been "a steady and patient hand at the wheel at a critical time in our history. He has served the people of NSW and the members of the Nationals with distinction, and I wish him and Cathy well in his retirement."