Former cabinet minister Sir David Lidington has announced he will stand down at the next general election.
The Aylesbury MP and former deputy to Theresa May said he wanted to devote more time to his family while he is "still active and in good health".
Sir David, 63, has held the safe Buckinghamshire seat since 1992 and said it has "a special place in my heart".
"Politics imposes a heavy cost on family and private life," he said.
Former Home Secretary Amber Rudd and former Conservative Party chairman Patrick McLoughlin have also decided to step down on 12 December.
South Cambridgeshire MP Heidi Allen also announced she would not seek re-election.
Sir David has held a variety of posts in the cabinet, including Leader of the House and Secretary of State for Justice.
He was also Minister of State for Europe under David Cameron.
The father-of-four said: "I have come to the conclusion that now is the right time for me to give a higher priority in terms of my time and energy to Helen and my family who have given unstinting support to me during more than a quarter of a century in the House of Commons."
He described serving his constituency as "an amazing privilege" and said he was grateful for the "support and confidence" of voters.
"Almost everyone that I have met in politics, whether at local or national level, has come into public life for the best of reasons: to try to change our country or our local area for the better," he wrote.
"My successor, whoever he or she may be, will be very fortunate to represent a constituency as diverse, lively and friendly as Aylesbury."