United Kingdom Secretary of State for Work and Pensions James Purnell announces his resignation and requests that Prime Minister Gordon Brown also resign. [http:--www.guardian.co.uk-politics-2009-jun-04-james-purnell-resigns-gordon-brown-cabinet "(Guardian)"]
- Former United Kingdom Cabinet Ministers Hazel Blears, James Purnell, John Hutton, and Caroline Flint coordinated their resignations to compel Prime Minister Gordon Brown to also resign.
- A report about the United Kingdom's involvement in the Iraq War is released. The chairman of the inquiry, Sir John Chilcot, said that the invasion was not a "last resort" and was based on "flawed intelligence and assessments". The inquiry was announced on 15 June 2009 by then-Prime Minister Gordon Brown. The final hearing was held on 2 February 2011.
- The process to elect a new leader of the Conservative Party to replace outgoing Prime Minister David Cameron begins in the United Kingdom. The Secretary of State for Work and Pensions Stephen Crabb is the first Conservative Party politician to announce his official candidacy for leader.
- British Prime Minister Gordon Brown travels to Cumbria to meet victims of the floods that have affected the area.
- Prime Minister of the United Kingdom Gordon Brown denies rumours concerning his health as the British Labour Party gathers for its conference in Brighton, expressing his amazement with Andrew Marr of the BBC for questioning him live on television.