Gareth Thomas was born in 1967 close to his Harrow constituency. He gained an economics degree from Aberystwyth then later studied history at King's College, London and qualified as a teacher at Greenwich University. He was a councillor in Harrow for seven years, and Labour group whip. In his maiden speech to the House of Commons he stressed that he had lived in Harrow all his life, and urged action on crime, housing and health.

Before his promotion to the Ministerial ranks, Gareth  chaired the All-Party Renewable Energy Group, campaigning for the introduction of emissions trading, a sustainable energy agency and greater help to boost the take up of energy efficiency and renewable energy.

Gareth introduced draft legislation to ban smoking in cafes and restaurants and has campaigned for electoral reform, for the introduction of compulsory voting (with a right to register an abstention) and for the alternative vote method of voting in elections.

Gareth also worked on a number of Standing Committees to deliver the Pollution Prevention and Control Bill, The National Lottery Bill, NHS Reform, Terrorism Bill, Regulation of Investigation Powers Bill and the Football Disorder Bill.

As well as this, Gareth successfully helped to steer the 'The Industrial and Provident Societies Bill' though Parliament, despite strong opposition from the Conservative Party. The Bill provides a more secure legal framework for community, cooperative and mutual organisations.

In 1999 he became Parliamentary Private Secretary to Charles Clarke, Minister of State at the Home Office. He stayed with him on his promotion to the Cabinet as Party Chairman in 2001 and as Education Secretary in 2002.

In 2003 he was promoted to Parliamentary Under Secretary of State, number two, at the Department for International Development. There he stayed under Gordon Brown as junior minister for trade policy, dividing his time between DfID and the new Department of Business, Enterprise and Regulatory Reform. He was promoted to Minister of State rank with the same dual brief in October 2008.

He has been chairman of the Co-operative Party since 2000, is a member of the Fabian Society, and has written on social responsibility and a low-carbon economy.

His hobbies include running, rugby union and supporting Harrow Borough Football Club and Arsenal Football Club.