He was a prominent member of the country's first generation of political leaders after Singapore became independent in 1965, serving as Deputy Prime Minister (1965–1968), Minister for Science and Technology (1968–1975) and Minister for Health (1975–1981). He served as the Chairman of the People's Action Party (PAP) from 1954 to 1981, and as the Vice-Chancellor of the University of Singapore from 1968 to 1975. After he left the Cabinet in 1981, he continued to serve as a Member of Parliament (MP) on the backbenches. He served as the Leader of the House from 5 June 1959 to 15 April 1968 until he retired from politics in 1988.