Kretz has been a member of Alliance 90/The Greens since 2009. From 2014 to 2016 he was a member of the district council of the Rhein-Neckar-Kreises district.
In the 2021 federal election, Kretz ran in the Rhine-Neckar federal constituency and in 19th place on the Green Party's state list in Baden-Württemberg, but initially missed out on entering the Bundestag. On 15 February 2024, he replaced Christian Kühn in the Bundestag when he resigned.[2] He has since been serving on the Committee on the Environment, Nature Conservation, Nuclear Safety and Consumer Protection.[3]
Other activities
German Institute for Development Evaluation (DEval), Member of the advisory board (since 2024)[4]