Britta Lejon has served as the President of The Union of Civil Servants (ST) in Sweden from 2012 to present, advocating for the rights and well-being of civil servants. She was also president of the National and European Administration Committee of the European region of PSI, EPSU, from 2015 to 2019.

Prior to her involvement in unions and administration, Britta Lejon was the President of the Swedish Library Organization from 2004 to 2009, where she contributed to the development and accessibility of libraries in Sweden.

She also served as a Member of Parliament from 2002 to 2006, where she was a part of the standing committee of Labour and the vice president of the standing committee of Justice. Her contributions in Parliament focused on labor issues and justice reforms.

From 1998 to 2002, Britta Lejon held a ministerial position in the Swedish Government, where she was responsible for Democratic Issues, Public Administration, and consumer Policies. During the Swedish Presidency of the EU in 2001, she led negotiations on transparency, resulting in the first EU legislation on the right of access to documents.

Earlier in her career, from 1994 to 1998, Britta Lejon served as the President of the civil servants in the Government offices of Sweden, showcasing her expertise in public administration. Prior to that, from 1990 to 1998, she worked as a Senior officer in the Ministry of Transport and Communication, contributing to the development of transportation policies.