Nigel Haigh studied engineering and practiced as a Patent Attorney  before moving to the environmental field in 1971. He helped to found the European Environmental Bureau in 1974 and was its Vice-President. In 1980 he opened the London office of IEEP when it was a network of offices in several countries with its head office in Bonn. He was a founder member of the Green Alliance and was its Chairman from 1989-98.  His book EEC Environmental Policy and Britain – an essay and a handbook ENDS 1984 was the first attempt to assess .the impact of the EEC on any Member State. It led to IEEP’s Manual of European Environmental Policy which he edited for many years. He was awarded an OBE in 1992 for services to environmental protection. He retired as Executive Director of IEEP in 1998 but remains an Honorary Fellow.

He served as a  Board member of the Environment Agency (England and Wales) 1995-2000, and on the Management Board of the European Environment Agency ( Copenhagen) as a nominee of the European Parliament (2000-2005). He was on the Editorial Board of the Journal of Environmental Law  and  an Honorary Research Fellow in the Department of Laws, University College London.

His book EU Environmental Policy – its journey to centre stage Routledge 2016  is a kind of history although he insists he is not a historian.

In 2024 he was appointed as a member of the College of Experts of the Office of Environmental Protection.