Tory MP Dan Byles is to stand down at the next election, forcing the party to find a new candidate to defend its most marginal seat.
Mr Byles, who won North Warwickshire with a majority of just 54 in 2010, said it was "time to move on to new challenges".
He said: "This has by no means been an easy decision, and I owe a great debt of gratitude to my parliamentary and constituency staff who have worked so tirelessly for the last four years on behalf of local people."
In a statement on his website Mr Byles, 40, said: "B efore becoming an MP I served in the Army for nine years, deploying on operational tours in Bosnia and Kosovo. By the time of the 2015 General Election, serving my country will have been the primary focus of my professional life for some 14 years.
"For myself and for my family, whose support and understanding have been unerring throughout, I believe it is now time to move on to new challenges. I will therefore not be standing for re-election in 2015.
"As I hoped it would be, my time in Parliament has been hard work but uniquely rewarding. I am proud of what we have achieved as a Government - putting Britain back on the road to recovery following the worst economic collapse the country has ever faced.
"I am particularly grateful for the personal contribution I have had the opportunity to make, as a member of the Energy and Climate Change Select Committee; chair of three active all-party parliamentary groups; on the Bill committee of the Energy Act 2014; and as the sponsor of an historic private members' Bill on House of Lords reform.
"With almost a year still to go before the general election, I remain absolutely committed to my constituents and to tackling the important issues that face us locally, such as HS2, ensuring that the George Eliot Hospital has a safe and secure future, and building on our recent successes in the local economy.
"It will be business as usual in North Warwickshire & Bedworth for Team Dan."