Mary Macleod served as the Member of Parliament for the Brentford and Isleworth constituency in West London from 2010-2015. She represented approximately half of the Hounslow Borough, covering Chiswick, Brentford, Syon, Osterley, Isleworth, Hounslow Central, Hounslow South and Hounslow Heath. During her time in Parliament she was also Parliamentary Private Secretary (PPS) to the former Culture Secretary, Rt Hon. Maria Miller MP, as well as to the former Policing Minister, Rt Hon. Nick Herbert MP and for the former Northern Ireland Secretary, Rt Hon. Theresa Villiers MP.

In addition, Mary held a number of other roles, including Chair of the All Party Parliamentary Group (APPG) Women in Parliament and Vice-President of the Commonwealth Youth Exchange Programme.