Among his jobs before becoming a cabinet member were consultant in the Ministry of Finance from 1946 to 1948, lecturer at the University of Oslo from 1947 to 1955, assistant secretary in the Ministry of Trade from 1948 to 1952, the same position at Statistics Norway from 1952 to 1954 and political chief editor in the newspaper Dagbladet from 1954 to 1965.

[1] In 1951 the idea of appointing Seip as a State Secretary in the Ministry of Finance was discussed, but it did not happen.

[6] He was secretary general of the Nordic Council from 1973 to 1977, and editor-in-chief of Norges Handels- og Sjøfartstidende (renamed Dagens Næringsliv in 1987) from 1977 to 1980.

He left in 1989 to become Data Protection Commissioner for the Council of Europe, a position he held until his retirement in 1995.

[1] His brother Martin Fredrik Seip was a noted physician and professor of medicine.