Former Prime Minister David Cameron is to stand down as MP for Witney, a role he held for 15 years.
The Conservative politician has held the post since June 7 2001 and was Prime Minister for six years of that time after he formed a coalition government with the Liberal Democrats in 2010.
Cameron said in a statement: "In my view, the circumstances of my resignation as Prime Minister and the realities of modern politics make it very difficult to continue on the backbenches without the risk of becoming a diversion to the important decisions that lie ahead for my successor in Downing Street and the Government.
"I fully support Theresa May and have every confidence that Britain will thrive under her strong leadership."
Cameron retained his position as Prime Minister last year after he promised a referendum on Britain's membership of the European Union in the wake of growing support for the UK Independence Party.
The ensuing referendum earlier this year resulted in Britain voting to leave the EU and Cameron resigned as leader of the Conservative party shortly afterwards, with Theresa May becoming Prime Minister after a brief leadership contest.
There will now be a by-election for Cameron's Witney seat.