New South Wales Nationals MP Adam Marshall is expected to face court next month charged with drink driving.

The Northern Tablelands MP was stopped and breath-tested by police at Glen Innes, in the state's north, on Friday night.

Officers say the 29-year-old was charged after returning a mid-range reading of 0.112.

Nationals leader and Deputy Premier Andrew Stoner says he is disappointed with the MP's actions and has accepted his resignation from the positions of Temporary Speaker and Deputy Chair of the State and Regional Development Committee.

Mr Marshall won his seat in a by-election last year, triggered by the resignation of Richard Torbay over allegations of corruption.

The MP has had his driver's licence suspended and will face Glen Innes Local Court on July 15.