24 January – The UK Supreme Court rules against the Government's Brexit appeal case by an 8 to 3 decision, stating that Parliament must vote to trigger Article 50.[4]
30 January – A petition to stop US President Donald Trump's UK state visit gathers more than 1.8 million signatures.[5]
8 February – Labour MP Clive Lewis resigns from the Shadow Cabinet in protest over his party's decision to whip its MPs into voting to trigger Article 50.[9]
23 February – By-elections are held in Copeland and Stoke-on-Trent Central to fill vacancies arising from the resignation of sitting Labour MPs. Trudy Harrison wins the Copeland seat for the Conservative Party and Gareth Snell retains the Stoke-on-Trent Central seat for the Labour Party. Labour had held the Copeland seat since its creation, and the Conservative win is the first gain by a serving government in a by-election for 35 years.[11]* 26 February – Father of the House of Commons and veteran Labour MP Gerald Kaufman passes away at the age of 86.[12]
14 March – The British Parliament passes the Brexit bill, paving the way for the UK Government to trigger Article 50; so that the UK can formally withdraw from the European Union.[15]
15 March – Chancellor of the Exchequer Philip Hammond is forced to make a U-turn on his commitment to raising National Insurance contributions for the self-employed after vast opposition from Conservative backbenchers.[16]
Theresa May formally rejects Scottish First Minister Nicola Sturgeon's second Scottish Independence Referendum timetable for Autumn 2018, or at least before Brexit negotiations are concluded.
20 April – The 2017 Manchester Gorton by-election is cancelled following the announcement of an impending general election. This was the first time a UK by-election had been cancelled since 1924.[23]
Local government elections are held across England, Scotland and Wales. The Conservative Party makes significant gains at the expense of the Labour Party, gaining 500 seats and seizing control of 11 councils. UKIP loses all 145 seats they were defending. The Liberal Democrats lose 41 seats, despite their share of the vote increasing. Labour is pushed into third place by the Conservatives in Scotland, where the SNP is comfortably the largest party despite failing to take control of target councils. The Conservatives win four out of six metro-mayoral areas, including in the traditionally Labour-voting Tees Valley and West Midlands.[25]
8 June – general election 2017: The Conservatives remain the largest party, but fail to get enough seats for a majority, leading to a hung parliament. In a surprise result, they are reduced from 330 to 318 seats. PMTheresa May rejects calls for her to resign and attempts to form a coalition with the DUP, which would give her 10 additional seats. Labour gain 32 seats, with particular success in London; the SNP suffers heavy losses with 21 fewer seats; the Liberal Democrats gain four seats for a total of 12; UKIP lose their sole seat and Paul Nuttall resigns as party leader.[27]
10 June – 10 Downing Street issues a statement claiming the Democratic Unionist Party have agreed a confidence-and-supply deal to support a Conservative minority government. However, both parties subsequently confirm that talks about an agreement are still ongoing.[28]
18 June – The Government announces that there will be no Queen's Speech in 2018, to give MPs more time to deal with Brexit laws.[30]
19 June – Brexit Secretary David Davis heads to Brussels as formal negotiations with the EU get underway.[31]
26 June – The Conservatives agree a £1 billion deal with Northern Ireland's Democratic Unionist Party to support Theresa May's Conservative minority government.[32]
27 June – Nicola Sturgeon announces that she will delay plans for a proposed second Scottish independence referendum.[33]
19 July – The government announces that a rise in the State Pension age to 68 will be phased in between 2037 and 2039, rather than from 2044 as was originally planned. This will affect 6 million men and women currently aged between 39 and 47 years old.[35]
22 July – Michelle Brown, UKIP member of the Welsh Assembly for north Wales, admits and apologises for using a racial slur in a telephone conversation, after her former assistant Nigel Williams released a recording of the call.[37]
26 July – The Supreme Court rules that employment tribunal fees are unlawful, meaning the government will have to repay up to £32m to claimants.[38]
3 November – Welsh Assembly minister Carl Sargeant is suspended by the Labour Party pending an investigation into allegations of sexual misconduct.[48] He is found dead four days later, having killed himself.[49]
7 November – Nicola Sturgeon, Scotland's First Minister, apologises to gay men convicted of sexual offences that are no longer illegal as new legislation is introduced that will automatically pardon gay and bisexual men convicted under historical laws.[50]
13 November – David Davis announces that Parliament will be given a vote on the final Brexit deal before the United Kingdom leaves the European Union in 2019.[51]
17 November – Sarah Clarke, current championship director of the All England Lawn Tennis Club, is appointed as the first female Black Rod. She will take up the position in January 2018, and have the title "The Lady Usher of the Black Rod".[52]
3 December – Alan Milburn and the entire Social Mobility Commission quit their roles, citing ‘lack of political leadership’, a repeated refusal to properly resource and staff the commission, an obsession with Brexit and an ‘absence’ of policy.[55][56]
13 December – After a rebellion by Conservative MPs, the government is defeated in a key vote on Brexit, with MPs voting in favour of giving Parliament a say on the final deal struck with the EU.[58]
14 December – The Scottish government's budget proposes splitting the 20% income tax band into three with a new lower band of 19%, a 20% band, and a 21% band for those earning over £24,000.[59]
20 December – The EU announces that the UK's Brexit transition period will end no later than 31 December 2020.[60]