Former transport minister Raymond Lim, 56, MP for East Coast GRC, will not contest in the coming general election.
Mr Lim told residents in his Fengshan ward at an event on Saturday night.
He said he is retiring to spend more time with his family and had informed Prime Minister Lee Hsien Loong of his decision.
He has identified a candidate who will be introduced in time, Mr Lim added.
He announced earlier on Aug 2 at a National Day dinner at Fengshan Community Club that the Government had approved the remaining HDB blocks in Fengshan to undergo the Home Improvement Programme, which will benefit close to 2,500 households. This means all eligible blocks in Fengshan will be upgraded, thus fulfilling a promise he made at the 2011 election, he said.
Fengshan has been carved out of East Coast GRC as a single-seat ward and the PAP is likely to face the Workers' Party in both.
Manpower Minister Lim Swee Say, who helms the PAP team in East Coast GRC, confirmed he will remain in the GRC.