Labour's Alan Johnson is to step down as an MP after the prime minister called for a general election in June.
In a letter to his constituents, the former home secretary said he would not be standing as a candidate in his Hull West and Hessle constituency.
Prime Minister Theresa May announced plans for a snap election on 8 June. A Commons vote will be held on Wednesday.
Mr Johnson, who has been an MP for 20 years, said he had to think about what was best for the Party.
"Every day has been a privilege and a pleasure but it can't go on for ever and the electoral cycle means that each incumbent has to think again about what's best for them, the constituency and the Party," he said in the letter.
"As far as the constituency and the Party are concerned, no MP wants to put them through the anguish of a mid-term by-election, so for me the personal decision is whether to retire now or in 2022 when I'll be into my 70s.
"I've decided that going now will give me the opportunity to do other things with my life and is therefore in the best interests of me and my family.
"I also think it's best for the Party."
However, in an earlier interview on BBC Radio Humberside on 20 March when asked if he would continue to be an MP after the next election, Mr Johnson had said he had "no intention whatsoever of stepping down, even at my great age".
The veteran Labour MP started working as a postman in London when he was 18, in 1968.
He eventually became general secretary of the Communication Workers Union before being elected as an MP.