SINGAPORE - Prime Minister Lee Hsien Loong has sent valedictory letters on Friday to three retiring ministers - Mr Lim Hng Kiang, Mr Lim Swee Say and Dr Yaacob Ibrahim - lauding them for their many contributions to Singapore over their decades of service.

Among the third-generation ministers, he knew Mr Lim Hng Kiang the longest - for over 40 years since they were students together at Cambridge University, noted the prime minister.

In the letter to the outgoing Trade and Industry Minister, Mr Lee described his approach to work is "hard-headed and practical, yet infused with a human touch".

"You are steady under pressure, analyse problems rationally and objectively, and have a sensitive feel for political considerations," Mr Lee wrote to the man who is leaving MTI after 14 years at the helm.

He added: "I and my colleagues will miss your pragmatic, farsighted approach to issues and your wise counsel in Cabinet."

Mr Lim has carried heavy responsibilities over the years, Mr Lee said.

As MTI chief, he built up key industry clusters in the manufacturing sector, including petrochemicals, semiconductors and life sciences, by promoting foreign investments and creating the right conditions for the sectors to grow.

He also worked hard to build trade relationships, as his team negotiated an extensive network of free-trade and partnership agreements for Singapore.

When the financial crisis hit in 2008, "your calmness and experience were pillars of strength," Mr Lee wrote.

"You systematically reviewed the options, and worked out a bold and effective package of measures, including notably the Special Risk-Sharing Initiative and Jobs Credit schemes. This response bolstered confidence, saved jobs, and enabled the Singapore economy to recover swiftly."

Mr Lee also praised Mr Lim's handling of the Sars crisis of 2003 as Health Minister.

"Amidst general fear and alarm, you assessed the situation and made sound decisions. After the crisis passed, the World Health Organisation praised Singapore's response to the outbreak."

In his letter to Mr Lim Swee Say, Mr Lee recalled how the outgoing Manpower Minister struck him as a " determined, passionate leader who delivered results", before Mr Lim had entered politics.

"You had a warm, down-to-earth personality. On the ground you were practical, persuasive and effective. I thought these attributes suited you to a political path, and so approached you to join politics in 1996," Mr Lee wrote.

Among Mr Lim's career highlights, Mr Lee pointed to the introduction of NEWater, "a game-changer in our water story".

Mr Lee noted that the challenge of NEWater "was not the science or engineering", but how to persuade Singaporeans to accept the idea of recycling and consuming used water, which he called a delicate matter of psychology and public confidence.

"This you achieved brilliantly," he wrote to Mr Lim, saying that the public's acceptance of NEWater has helped Singapore "substantially overcome a strategic vulnerability that has obsessed us ever since independence".

Mr Lee also noted that as Manpower Minister, Mr Lim had a strong understanding of the labour market, and how to balance the interests of workers with the needs of businesses.

"You managed the strong political pressures on our foreign worker policies, and prioritised the Singaporean core of our workforce," he said.

He also praised Mr Lim's ability to come up with vivid catchphrases that have clung on to Singapore's collective memory over the years, such as "cheaper, better, faster", "better, betterer, betterest", "futurise" and most recently, "1/3 + 2/3 >1" to describe the local workforce composition.

"These were not idle wordplay or poor math, but embodied important economic and manpower realities and priorities in a form that Singaporeans could understand, remember and act upon," Mr Lee said.

In his letter to Dr Yaacob, Mr Lee highlighted the important role that the outgoing Minister-in-charge of Muslim Affairs has played in helping the Government to handle sensitive issues involving race and religion.

On such matters, Mr Lee said, "I could rely on you to understand the national imperatives, present forthrightly the Malay/Muslim point of view, and advise me candidly on how best to move forward with the support of the community".

Dr Yaacob also made lasting contributions to the support structures for the local Muslim community, Mr Lee said.

He also recalled how in one of Dr Yaacob's first Parliamentary speeches as Acting Minister, he said that "one can be a good Muslim and a good citizen".

"This set an important direction for Singapore Muslims," Mr Lee wrote. "You have worked hard to lead the community to look forward, to integrate with non-Muslim Singaporeans, and to adapt and change with the times."

Dr Yaacob, who is also the outgoing Communications and Information Minister, also pushed for investment in infrastructure, so today Singapore has one of the highest broadband speeds and internet penetration rates in the world.

At the same time, Mr Lee noted, Dr Yaacob made sure that no one was left behind by the new technology.

"You implemented programmes to develop capabilities and promote the adoption of digital technologies especially among the small medium enterprises," he said.

"You also launched programmes to teach digital skills to seniors, and to help lowincome families receive digital TV and connect to the Internet."

The three ministers will step down from their roles on April 30.

Their retirement was announced on Tuesday as part of a wider Cabinet reshuffle which saw more fourth-generation leaders stepping up to lead in key Government roles.