In 2004, Hillier was
selected as the Labour
prospective parliamentary candidate to contest
Hackney South and Shoreditch through an
all-women shortlist. At the
2005 general election, she was elected to the
House of Commons as MP for Hackney South and Shoreditch, winning with 52.9% of the vote and a majority of 10,204. Hillier 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. During maternity leave beginning in March 2009, her ministerial role was taken over by
Shahid Malik. In March 2008, Hillier voted with the Government in favour of nationwide Post Office closures, including seven in
Hackney, of which her constituency forms a part. In December 2009, while promoting the
National Identity Card scheme as Identity Minister in
Liverpool, she admitted she had forgotten her own ID card, attributing the error to the demands of looking after her baby. At the
2010 general election, Hillier was re-elected as MP for Hackney South and Shoreditch with an increased vote share of 55.7% and an increased majority of 14,288. She was again re-elected at the
2015 general election with an increased vote share of 64.4% and an increased majority of 24,213. In June 2015, Hillier was elected Chairman of the
Public Accounts Committee (PAC) 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. An ardent supporter of the Remain campaign during the
2016 EU referendum, Hillier announced that she was "devastated" that the
United Kingdom voted to leave the European Union and that the decision was fuelled by "
xenophobic undertones". She supported
Owen Smith in the failed attempt to replace
Jeremy Corbyn in the
2016 Labour Party leadership election. Hillier was again re-elected at the
snap 2017 general election with an increased vote share of 79.4% and an increased majority of 37,931. She stood for election as
Speaker of the House of Commons during the
2019 Speaker election. However, she was unsuccessful, securing 10 votes (or 1.8%) in the first round, and coming in 7th out of seven candidates. At the
2019 general election, Hillier was again re-elected, with a decreased vote share of 73.3% and a decreased majority of 33,985. Hillier was appointed
Dame Commander of the Order of the British Empire (DBE) in the
2021 Birthday Honours for political and parliamentary service. At the
2024 general election, Hillier was again re-elected, again with a decreased vote share of 59.3 and a decreased majority of 14,737. She was elected unopposed as chair of the
Treasury Select Committee on 9 September 2024. ==Personal life==