Rees joined the Labour Party in 1982 and has been an active member ever since. He has held several positions within the Labour Party and was the Constituency Labour Party secretary for Aberavon between 2005 and 2011. and in the
2007 election for the
South Wales West region, where Labour earned no regional top-up seats, meaning he was not elected. He is a member of both
Unite and
Unison trade unions. Throughout his working life he has been a strong advocate for good working relationships with the trade unions and regularly raises trade union issues in the Senedd. Rees is currently chair of the Committee for the Scrutiny of the First Minister, the Llywydd's Committee and the
Reform Bill committee. He has previously chaired the External Affairs and Additional Legislation Committee and the Health and Social Care Committee. In the
2026 Senedd election, he will be a candidate in the
Afan Ogwr Rhondda constituency. He will be third on the party list behind
Huw Irranca-Davies and
Buffy Williams. ==References==