 Nordtun held various positions in Stavanger city council from 1979 to 1995, serving as deputy mayor in 1987–1989 and mayor from 1990 to 1993.From 1986 to 1990 he was also a member of Rogaland county council.He chaired the city party chapter from 1989 to 1994, and was a member of the Labour Party national board from 1991 to 2003.