Since 2015 Stephen has been the Labour Member of Parliament for Aberavon in the House of Commons, UK Parliament. In April 2020, Stephen was promoted to Shadow Foreign Office Minister for Asia and the Pacific. In addition to this Stephen is currently a member of the Committee on the Future Relationship with the European Union; Chair of the All Party Parliamentary Groups for Post Brexit Funding for Nations, Regions and Local Areas and Reuniting Britain Post Brexit; Secretary of the All Party Parliamentary Group for Steel and Metal Related Industries. He is also the Parliamentary Chair of Labour Business.

Stephen is the author of ‘A New Nation: Building a United Kingdom of Purpose, Patriotism and Resilience’, Policy Press (2015) and Co-author of ‘Spirit of Britain, Purpose of Labour’, Labour Future Ltd (2018).