Jean Lambert was first elected to the European Parliament in 1999 as the Green Member for London, representing the views of those who want an environmentally sustainable fairer society. Jean was member of the EP Committee on Employment and Social Affairs where she focused on social inclusion, workers' rights, immigration, social security and the European Semester process. She also seated at the EP Committee on Civil Liberties, Justice and Home Affairs, where she worked on issues related to asylum, immigration, children's rights and anti-discrimination. Jean campaigned for the UK to Remain a member of the European Union and is now working to ensure that the UK exit from the EU does not harm the future of London, the UK or the EU.

Jean is a Committee Member of the European Green Party.