In May 2009 Lumley supported the Green Party during the 2009 European Elections campaign. For Lumley, the work of Green MEPs in the European Parliament in pursuing human rights and animal rights made the Green Party "the obvious choice" and urged UK voters "to cast a positive vote for a better future by voting Green in the European Elections." Lumley also appeared in literature to support changing the British electoral system from first-past-the-post to alternative vote for electing Members of Parliament to the House of Commons in the Alternative Vote referendum in 2011.