Margaret Olivia Hillier (born 14 February 1969) was first elected as the Member of Parliament (MP) for Hackney South and Shoreditch at the 2005 general election, and was a junior government minister (2007–10) and was succeeded by Caroline Flint as Shadow Secretary of State for Energy and Climate Change in the Labour Party October 2011 reshuffle.
In 2004, Hillier was selected as the Labour candidate to contest the Hackney South and Shoreditch through an all-women shortlist. She was elected to the House of Commons at the 2005 general election following the retirement of the Labour MP Brian Sedgemore.
During the election campaign, Sedgemore resigned from Labour and joined the Liberal Democrats in protest at the attack on Iraq. Hillier retained the safe seat with a majority of more than 10,000 votes. She made her maiden speech on 24 May 2005, noting there were more men in the House of Commons that day than there had ever been women MPs.
She served as member of the Northern Ireland Affairs Select Committee for a year until she was appointed Parliamentary Private Secretary to the Secretary of State for Communities and Local Government Ruth Kelly in 2006. In June 2007, she was appointed a Parliamentary Under-Secretary of State at the Home Office.
In June 2015, Hillier was elected Chairman of the Public Accounts Committee in succession to Margaret Hodge. She was, as a result, among the 100 most influential people in the NHS according to the Health Service Journal in 2016. As chair, she has been critical of the Troubled Families programme, saying that the PAC's conclusions on the programme were "far more serious" than "a slap on the wrist" for ministers.
Hillier has served Trustee of the War Memorials Trust since 2001.