Falconer became the Lord Chancellor and the first Secretary of State for Constitutional Affairs in 2003 under Prime Minister Tony Blair, and would go on to become the first Secretary of State for Justice in a 2007 reorganisation and enlargement of the portfolio of the Department for Constitutional Affairs. He held this role for over a month until Gordon Brown became Prime Minister in June 2007. Falconer was named Shadow Justice Secretary under the acting leadership of Harriet Harman in 2015, and continued in this role after the election of Jeremy Corbyn as leader of the party, until—along with dozens of his colleagues—he resigned on 26 June 2016. He was appointed as Shadow Attorney General in the Starmer Shadow Cabinet on 6 April 2020.