Caroline is co-leader of the Green Party with Jonathan Bartley as well as its first MP, representing Brighton Pavilion. She served as an MEP from 1999 until 2010 and as an Oxfordshire councillor previously.

She is Co-Chair of the All Party Parliamentary Group on Fuel Poverty, as well as Vice Chair of the Animal Welfare, Public and Commercial Services, Sustainable Housing and CND All Party Parliamentary Groups. She is also a member of the Parliament's Environmental Audit Committee.

Caroline continues to be an active campaigner on a range of issues and has been voted the UK's most ethical politician in 2007, 2009 and 2010 by readers of the Observer. She is also in the Environment Agency's Top 100 Eco-Heroes of all time.