Witney MP Robert Courts congratulated the new prime minister Rishi Sunak and said it is "now time to unite" for difficult times.
He said: “Rishi will restore unity and provide calm, competent and professional leadership during these challenging times. He will deliver stability and economic confidence, ensuring we can take our country forward and deliver upon our 2019 mandate.”
Liz Truss announced she would step down from the role on October 20 after just 45 days, making her the UK's shortest serving Prime Minister.
Mr Sunak was guaranteed the job when Penny Mordaunt pulled out of the leadership race.
Before the announcement of Mr Sunak's appointment, Mr Courts tweeted: "Our urgent tasks are to restore stability in government and provide economic confidence in challenging times.
"We need strong, competent leadership in No.10 to take our country forward and deliver our 2019 mandate. @RishiSunak is undoubtedly the person to provide this leadership."
Both Liz Truss and Rishi Sunak visited West Oxfordshire Conservatives over the summer during the leadership contest.
In July Tory leadership hopeful Rishi Sunak addressed members of the party in Witney.
West Oxfordshire Conservative Associaton welcomed Tory leadership hopeful Liz Truss to Carterton in August.
