Mark was a Conservative Party whip between November 2006 until July 2007 and as a Shadow Minister for DfID until the 2010 General Election.
Shortly after his re-election in 2010, he was appointed as the Parliamentary Private Secretary (PPS) to the Secretary of State for International Development. In September 2012 he became a Government Minister when he was made a Lord Commissioner of Her Majesty’s Treasury.
In May 2015, following his re-election, Mark was appointed Minister for Defence Veterans and Personnel. In June 2016 he had the Reserves added to his portfolio. Responsibilities currently include the Armed Forces Covenant, Service and civilian personnel, reserves, cadets, veterans, Service families and Defence Infrastructure.
Following the General Election in June 2017, Mark was appointed to Minister of State for Armed Forces.