She was lijsttrekker for the Labour Party in the Dutch Senate election of 2011 and 2015. From 7 June 2011, she was a member of the Senate as well as Senate group leader of the Labour Party. She stepped down as member of the Senate on 8 February 2018, after a controversy about her vacation during a Senate debate."PvdA-fractievoorzitter in de Eerste Kamer Marleen Barth treedt af", Parlement & Politiek, 8 February 2018.
