Keir Starmer served as Leader of the Opposition from April 2020, following the resignation of Jeremy Corbyn after Labour's defeat at the 2019 general election and Starmer's election as Labour leader in the ensuing leadership election, until his party won a landslide victory at the 2024 general election in July 2024. During his tenure, Starmer moved Labour toward the political centre and emphasised the elimination of antisemitism within the party. Membership of the party under Starmer's leadership has more than halved: it fell from 550,000 in 2020 to 370,000 by 2023, and continued to fall in the following years, reaching 250,000 by the end of 2025.

Having become Leader of the Opposition amid the COVID-19 pandemic, Starmer said in his acceptance speech that he would refrain from "scoring party political points" and would work with the government "in the national interest". He later became more critical of the government's response to the pandemic following the Partygate scandal. Amid the historic number of ministers resigning from Boris Johnson's government in July 2022, Starmer proposed a vote of no confidence in the government, stating that Johnson could not be allowed to remain in office given the large-scale revolt by his own ministers. Starmer also criticised Johnson's government, as well as the governments of his successors Liz Truss and Rishi Sunak, for issues such as the Chris Pincher scandal and subsequent government crisis, the economic crisis resulting from the 2022 mini-budget and subsequent government crisis, the cost of living crisis and the National Health Service strikes and other industrial disputes and strikes.

As Labour leader, Starmer focused on repositioning the party away from the left, promising of economic stability, tackling small boat crossings, cutting NHS waiting times and ''rebuilding the NHS'', worker rights enrichment, energy independence and infrastructure development, tackling crime, improving education and training, reforming public services, renationalising the railway network, and recruiting 6,500 teachers. Starmer also pledged to end antisemitism in the party. During his time in office, Starmer was accused by members of his own party of marginalising the Labour left and denying genocide in Gaza. Under his leadership, Corbyn was expelled from the party. Labour made significant gains in the 2023 and 2024 local elections, and won a landslide victory in the 2024 general election. After Starmer became Prime Minister, he was succeeded as Leader of the Opposition by Sunak.

Background Keir Starmer was selected in December 2014 to be the Labour parliamentary candidate for the Labour UK constituency of Holborn and St Pancras, a safe seat, following the decision of the sitting MP Frank Dobson to retire. Starmer was elected at the 2015 general election with a majority of 17,048. Following Corbyn's win in the 2016 Labour leadership election in September, Starmer accepted a new post under Corbyn as Shadow Secretary of State for Exiting the European Union.

In the 2019 general election, Labour suffered its worst election defeat since 1935, with the Conservative Party earning an 80-seat majority. Labour won 203 seats, gaining 32.2% of the vote. This was the Labour Party's fourth consecutive general election defeat. Following Labour's defeat, Corbyn announced that he would stand down as Leader of the Labour Party. Starmer began to distance himself from Corbyn's leadership and many of the policies he put forward at the election, revealing in 2024 that he was "certain that we would lose the 2019 election". Following the party's defeat at the 2019 election, Corbyn announced that he would stand down as Leader of the Labour Party following a "process of reflection".

Labour leadership bid

On 4 January 2020, Starmer announced his candidacy for the 2020 Labour Party leadership election, following the resignation of Jeremy Corbyn after Labour's defeat at the 2019 general election. By 8 January, it was reported that Starmer had gained enough nominations from Labour MPs and MEPs to get onto the ballot paper, and that the trade union Unison was backing him. Unison, with 1.3 million members, said Starmer was the best placed candidate to unite the party and regain public trust. He also gained support from former Labour Prime Minister Gordon Brown and Mayor of London Sadiq Khan.

During the leadership election, Starmer ran a left-wing platform. He positioned himself in opposition to austerity, stating that Corbyn was "right" to position Labour as the "party of anti-austerity". He indicated he will continue with the Labour policy of scrapping tuition fees as well as pledging "common ownership" of rail, mail, energy and water companies and called for ending outsourcing in the NHS, local governments and the justice system. Supporters of Rebecca Long-Bailey criticised Starmer for releasing details of his campaign donations on the register of members' interests rather than independently, as Long-Bailey and Lisa Nandy had done, which meant that some details of his donors were not published until after the election had ended. Starmer went on to win the leadership contest on 4 April 2020, defeating Long-Bailey and Nandy, with 56.2% of the vote in the first round, and subsequently became Leader of the Opposition.

Tenure as Leader of the Opposition

Having become the Leader of the Opposition amid the COVID-19 pandemic, Starmer said he would refrain from "scoring party political points" and would work with Boris Johnson's government "in the national interest". He later became more critical of the government's response to the pandemic following the Partygate scandal. Starmer also criticised Johnson's government, as well as the governments of his successors Liz Truss and Rishi Sunak, for issues such as the Chris Pincher scandal and subsequent government crisis, the economic crisis resulting from the 2022 mini-budget and subsequent government crisis, the cost of living crisis and the National Health Service strikes and other industrial disputes and strikes. Amid the historic number of ministers resigning from Johnson's government in July 2022, Starmer proposed a vote of no confidence in Johnson's government, stating that Johnson could not be allowed to remain in office given the large-scale revolt by his own ministers. Starmer's questioning strategy against Johnson, Truss and Sunak was similar to that of a prosecutor.

Policies Starmer's tenure saw the party move closer towards the political centre. Speaking at the party's annual conference in 2021, the first time Starmer addressed the annual conference in person since becoming the leader, he presented his focus on stronger economy and tougher stances on crime, repositioning the party away from the previous leadership. By 2022, Starmer had dropped most of the socialist policies he advocated during his leadership run, including pledges made to nationalise water and energy, scrap tuition fees, and defend free movement within the EU. Starmer responded to criticism in 2023 by stating that they remained "important statements of value and principle", but cited the COVID-19 pandemic, the Russian invasion of Ukraine and the economic crisis resulting from the 2022 mini-budget as having meant that these pledges have had to be adapted.

Under Starmer's tenure, the party still supports the renationalisation of Britain's railways, and has pledged to create a publicly owned energy company, Great British Energy, to "compete with private industry and promote clean energy", differentiated from full nationalisation of the energy industry as previously pledged. In February 2023, Starmer set out five "national missions" as the basis for Labour's manifesto for the 2024 general election: achieving the highest sustained growth in the G7 by the end of his first term, establishing the UK as a "clean energy superpower" with zero-carbon electricity by 2030; enacting health and care reform, improving the justice system, and dismantling the barriers to opportunity" with education and childcare reforms. Upon becoming Labour leader, he tasked Brown with recommending British constitutional reforms. The report was published in 2022 and was endorsed and promoted by Starmer, and recommended the abolition of the House of Lords, extending greater powers to local councils and mayors, and deeper devolution to the countries of the United Kingdom. In November 2022, Starmer said that he would strip politicians of the power to appoint people to the House of Lords in the first term of a Labour government, adding that the public's trust in the political system had been undermined by successive Conservative leaders granting peerages to "lackeys and donors". Labour's 2024 election manifesto Change, however, did not recommend abolition to the House of Lords, instead committing only to removal of the remaining hereditary peers from the chamber, setting a mandatory retirement age of 80, and beginning a consultation on replacing the Lords with a "more representative" body.

Antisemitism reforms

Following past accusations of new antisemitism in the party during Corbyn's tenure, Starmer pledged to end antisemitism in the party during his acceptance speech, saying "Anti-semitism has been a stain on our party. I have seen the grief that it's brought to so many Jewish communities. On behalf of the Labour Party, I am sorry. And I will tear out this poison by its roots and judge success by the return of Jewish members and those who felt that they could no longer support us."

In April 2020, an internal party report on antisemitism (The Work of the Labour Party's Governance and Legal Unit in Relation to Anti-semitism, 2014–2019) was leaked. It was made during the end of Corbyn's leadership, intended for submission to the EHRC, and dated March 2020. It detailed that there was a tangible issue with antisemitism in the party, but factional hostility to Corbyn hampered efforts to tackle it. In January 2023, it was reported that the Information Commissioner's Office (ICO) were not going to take action against the Corbyn-supporting authors of the report, which leaked with unredacted confidential information, and that the Labour Party would pursue a civil case against them. This internal report led to the Forde Report.

In October 2020, following the release of the Equality and Human Rights Commission (EHRC)'s report into antisemitism in the party, Starmer accepted its findings in full and apologised to Jews on behalf of the party. The report said that there was "a culture within the party which, at best, did not do enough to prevent antisemitism and, at worst, could be seen to accept it". The report also found that the party had broken equality laws due to the handling of antisemitism complaints. Starmer added that the findings were "hard to read" and that it had "been a day of shame for the Labour Party".

Later that day, Corbyn stated that "the scale of the problem was also dramatically overstated for political reasons". He was later suspended over his response to the report. Some on the left of the party called for Corbyn's suspension to be lifted. On 14 November 2022, it was reported that the leadership of the Labour Party would not restore the whip to Corbyn, preventing him from standing for election on behalf of the Labour Party. This led to speculation Corbyn could stand for election as the Mayor of London or in his current parliamentary constituency as an independent candidate, in opposition to Labour. In March 2023, Labour's National Executive Committee (NEC) voted 22 to 12 on a motion from Starmer to prevent the Labour Party from endorsing Corbyn as a candidate for the party at the next general election.