SINGAPORE - Emeritus Senior Minister Goh Chok Tong, 79, is retiring from politics after 44 years as a Member of Parliament.

Mr Goh, who was prime minister from 1990 to 2004, announced his decision in a letter to Prime Minister Lee Hsien Loong on Wednesday (June 24) and PM Lee has accepted his decision to retire from politics.

In his reply on Thursday (June 25), PM Lee thanked Mr Goh for a lifetime of distinguished service, on behalf of all Singaporeans.

The exchange of letters was released by the Prime Minister's Office on Thursday.

Mr Goh said it has been his greatest honour and privilege to have served the People's Action Party, residents of Marine Parade, as well as Singapore and Singaporeans over the past 44 years. He added that he will continue to contribute in other ways.

In a Facebook post on Thursday afternoon, Mr Goh said: "Residents, party comrades and grassroots leaders have urged me to stand once more in the coming GE. It is with a heavy heart that I have decided not to. Although I am still healthy, I worry I will not have the same energy to serve after I become an octogenarian next year (sounds old, doesn't it?). It will not be fair to you."

Mr Goh assured residents that Marine Parade will be in "very capable hands" under his successor in the constituency, Dr Tan See Leng.

Mr Goh said Dr Tan, 55, who has been understudying him for two years, has the "right character, temperament, motivations, values and competence to be your next MP". Dr Tan will succeed Mr Goh as PAP Marine Parade Branch chairman.

In his reply to Mr Goh's letter, PM Lee said he is glad Mr Goh's succession is well in hand. Said PM Lee: "It is in Marine Parade that you have left the most personal imprint on the lives of individual Singaporeans. You were returned as the MP for Marine Parade eleven times, in ten general elections and one by-election over almost 45 years.

"When you were first elected in 1976, Marine Parade was newly reclaimed land - a large but blank canvas on which our hopes and dreams could be projected. Today, those dreams have become reality. Marine Parade has become a vibrant waterfront town filled with warmth, which people of all ages are proud to call home," PM Lee wrote.

"The story of Marine Parade is the story of Singapore - out of nothing, we created something special. You made that happen."

PM Lee acknowledged how Mr Goh had continued to contribute to Singapore's growth after he stepped down as PM - from inculcating the values and ethics of public service in younger MPs to guiding the Monetary Authority of Singapore (MAS) to enhance the resilience of the banking system, strengthen links with international partners, promote innovation, and protect retail consumers.

PM Lee also recognised Mr Goh's efforts in building good relationships with foreign leaders which in turn created opportunities for Singapore businesses.

In a Facebook post on Thursday, PM Lee added: "I am forever personally indebted to Chok Tong, who brought me into politics. Ours was a fruitful comradeship that spanned the entirety of my years in politics and most of his - a close friendship between two prime ministers that would be the envy of many countries."

Deputy Prime Minister Heng Swee Keat, in a Facebook post, recalled how Mr Goh had given him very valuable advice during the Global Financial Crisis in 2008, when he was deliberating hard on whether to seek approval from the President for a $150 billion guarantee on all bank deposits in Singapore, to be backed by past reserves.

Mr Heng was then the managing director of MAS and Mr Goh its chairman.

"I was glad to have the wise counsel of ESM Goh. He taught us that we must face difficult decisions head-on. Having thought through the options, we must have the courage to do what is right. It was a lesson that stayed with me and continues to guide much of my work," wrote Mr Heng.

In a Facebook post, Speaker of the 13th Parliament Tan Chuan-Jin thanked Mr Goh for being a great mentor, describing him as a "down-to-earth person with a mischievous sense of humour" who looks out for those around him and his residents.

Mr Goh, an economist by training, joined the Government's Administrative Service in 1964 and joined national shipping company Neptune Orient Lines in 1969, becoming its managing director from 1973 to 1977.

He entered politics in 1976 and was first elected to Parliament as MP for Marine Parade in the 1976 general election.

He was re-elected in nine subsequent general elections, and served as Minister for Trade and Industry, Health and Defence between 1979 and 1990. He was appointed Deputy Prime Minister in 1985, and succeeded Mr Lee Kuan Yew as Singapore's prime minister in November 1990.

Mr Goh relinquished the post of PM in August 2004 to Mr Lee Hsien Loong, and remained in the Cabinet as Senior Minister. He also served as chairman of MAS from 2004 to 2011.

He stepped down from Cabinet alongside Minister Mentor Lee Kuan Yew after the 2011 general election, and was given the honorary title of Emeritus Senior Minister.

He was also appointed Senior Advisor to MAS.

His successor in Marine Parade, Dr Tan, was introduced as a PAP candidate for the July 10 general election on Thursday morning by Mr Heng. Dr Tan, who was former group chief executive and managing director of IHH Healthcare, is a medical practitioner with more than 30 years of experience in the healthcare industry.