Steven was elected as MLA for North Down in May 2011.
He currently serves on the Enterprise, Trade and Investment Committee where it is his responsibility to hold the Minister of the Department of Enterprise, Trade and Investment to account.
He is Chair of the Assembly All Party Group on Co-operatives and Mutuals and Chair of the All Party Group on Renewable Energy. He also sits on the All Party Groups on Children & Young People, Ethnic Minority Communities and International Development.
After meeting former Green Party Leader John Barry at a protest march against the invasion of Iraq, Steven decided to join the Green Party in 2003.
He stood for the Greens in the European elections in 2009 when the party secured their biggest ever vote in Northern Ireland. A year later he was the first Green Party member to contest the Westminster election in North Down and became Leader of the Party the following year.