Temasek Holdings chairman S. Dhanabalan, 75, is retiring after 17 years as chairman of the Singapore investment company.

His successor is former labour chief Lim Boon Heng, 65, who will take over on August 1.

Mr Dhanabalan, who had a sterling career as a Cabinet minister and chairman of both DBS and Singapore Airlines, leaves on a high note as the value of Temasek's portfolio rose to a fresh record of $215 billion as at March 31 this year.

But he noted that the board and management are aware that Temasek "cannot remain where it is" and said his successor will face challenges in keeping the portfolio of investments on "a steady trend" in an increasingly volatile world.

Mr Dhanabalan said that in choosing Mr Lim, the board unanimously selected a candidate who has experience in both the private and public sectors, and who is adaptable, learns quickly and is able to build rapport with people.

"I have been looking forward to my retirement, and I am delighted that Boon Heng will succeed me in taking Temasek into its next phase of growth. His experience in both the public and private sectors, as well as his people-orientation and leadership experience, will be of immense value and relevance as chairman of Temasek," he said.

Mr Lim started his career in shipping firm Neptune Orient Lines before serving more than 30 years in politics where he was secretary-general of the National Trades Union Congress and Minister in the Prime Minister's Office. He left politics in 2011 and joined the Temasek board in June last year.

Mr Lim said in a media statement: "Temasek is a key Singapore institution, and an Asia-focused investment house. It has a portfolio of strong companies and a remarkable team of global talent... I am very honoured to have this opportunity to work with the board and management to take the company forward."