David Lewis received his training in economics from the Universities of the Witwatersrand and Cape Town. Between 1975 and 1990 he worked in the trade union movement, serving as General Secretary of the General Workers Union.
From 1990, Lewis directed the Development Policy Research Unit, a UCT based research group specialising in trade and industrial policy. Between 1994 and 1996 he served as Special Advisor to the Minister of Labour and co-chaired the Presidential Commission on Labour Market Policy.
Lewis was a member of the ministerial team tasked with the development of competition policy and with drafting the Competition Act. Between 1999 and 2009 he served for two terms as chairperson of the Competition Tribunal. He served on the Steering Group of the International Competition Network from 2001 until 2009 and Chairman of the Steering Group from 2008-9.
Lewis has served on the boards of the National Research Foundation, the International Marketing Council of South Africa, the Johannesburg Development Agency, South African Airways and the Industrial Development Corporation. He was deputy chairman of the board of the IDC from 2002-2008.
In 2009, Lewis was appointed an extraordinary professor at the Gordon Institute of Business Science. In 2010 he was awarded an honorary doctorate in economic sciences by the University of Cape Town.
In 2011, he was instrumental in the establishment of Corruption Watch, a non-governmental organization, of which he is the Executive Director.