Terry Redman is tipped to become the new WA Nationals Leader after Brendon Grylls confirmed his intention to step down from the leadership and the ministry.
A formal parliamentary National Party process will now commence to elect a new leader.
Mr Grylls took on the leadership of the WA Nationals in 2005 after successfully challenging Max Trenorden for the role.
The ABC understands Mr Grylls will stay on as the member for Pilbara.
He will outline his reasons for standing down from the leadership and the ministry at a media conference on Monday.
Mr Grylls has a young family which could be a reason for his resignation.
The Premier Colin Barnett is a supporter of the Nationals’ deputy Leader Terry Redman, who Mr Grylls has previously tipped to be his successor.