With the year-old Labour Government struggling on multiple fronts, there has been growing excitement about the prospects of former Labour leader Jeremy Corbyn’s new party capturing Labour’s left flank. However, while history suggests such breakaway movements rarely endure, by energising the disillusioned and peeling away key groups of voters, his new movement risks worsening the internal divide within the Labour Party and forcing the party to confront its future direction.
Despite Labour’s landslide 174-seat majority at the July 2024 General Election, Labour remains highly vulnerable to a challenge, especially one from its left.
When Sir Keir Starmer successfully contested the Labour leadership in 2020, many supporters believed they were getting a softer version of Jeremy Corbyn’s radicalism — “Corbynism without Corbyn”. His leadership campaign leaned left, promising bold climate action, public ownership, the abolition of tuition fees and a break from austerity politics. But soon after becoming Leader, Starmer pivoted decisively to the centre, prioritising fiscal restraint and incremental reforms while marginalising key left-wing figures, including Corbyn himself. For much of the Labour left, this amounted to betrayal: commentators such as Owen Jones left the Party and openly argued that Labour had become a “hostile environment” for those of his ideological persuasion.
Starmer’s centrist pivot may have helped him secure the largest parliamentary majority since 1997, but it also delivered the lowest vote share for a governing majority since the Second World War. His failure to inspire either the left or the right meant that this majority was built on fragile foundations. Despite winning 63% of seats in the Commons, Labour only won 33.7% of the vote. In 131 seats, its majority was under 5,000 votes. The result was a triumph of seat arithmetic rather than broad-based enthusiasm, meaning, as was pointed out at the time, that its majority was “broad but shallow”.
While a successful premiership might have helped to reconcile disgruntled left-wingers to the Starmer project, a series of blunders has only widened the rift between them. Political missteps such as restricting winter fuel payments to only the poorest pensioners sparked widespread criticism. Policy reversals on disability benefit reforms, and failure to meet ambitious housing targets have frustrated Party members, supporters and MPs alike. Additionally, Labour’s handling of the Gaza conflict and its early support for Israel drew sharp criticism from within the Party, especially among Muslims and younger voters. Such is the depth of the Government’s difficulties that Deputy Prime Minister Angela Rayner has privately warned colleagues that they have just 12 months to save the government’s credibility.
The damage is visible in polling. A July YouGov survey placed Starmer’s net approval at —44 (23% positive, 67% negative). Within the Party, 64% of members want the party to adopt a more left-wing platform, even though 61% also recognise the need for electoral compromise. Labour faces a strategic crossroads: shift left to reclaim dissatisfied voters or double down on centrism to appeal to the broader electorate. The ideological tug of war has created a fertile ground for Corbyn’s new movement.
Seizing his moment, Corbyn, together with fellow former Labour MP Zarah Sultana launched his new party in June 2025. Despite not yet even having a name, it quickly claimed 600,000 sign-ups and has even polled close to 20% in some surveys.
Yet history shows how steep the path is for new parties. The SDP-Liberal Alliance polled above 25% in the 1983 election, yet due to the first-past-the-post system, secured only 23 MPs with 25.4% of the national vote, many of them liberals, and ultimately dissolved into the Liberal Democrats. Corbyn’s movement risks a similar fate. Without durable grassroots infrastructure and a pipeline of credible candidates, it could flare up and fade quickly.
Even if it survives, its coalition looks fragile. Early polling suggests much of its appeal lies among younger, socially liberal voters disillusioned with Labour: with one Ipsos survey finding that 33% of 16-34 year olds would consider voting for Corbyn’s party, compared to just 9% of over-55s. But this demographic is fragmented and often issue-specific. While the party champions anti-austerity policies and public ownership, its liberal stance on social issues may clash with the more socially conservative Muslim voters who might otherwise be attracted by its position on Gaza.
Rather than breaking the mould of British politics, its impact is likely to come from splitting Labour’s vote. Like the SDP in the 1980s, it could hand marginal seats back to the Conservatives or Reform UK, paradoxically strengthening the right by fracturing Labour’s coalition. Corbyn’s movement doesn’t need to succeed outright, it only needs to chip away at Labour’s fragile base to weaken the left as a whole.
In short, Labour is fracturing. Starmer’s shift to the centre alienated the left before he even entered government, and in power he has failed to deliver victories that might have reconciled them to this pivot. Corbyn’s party may prove short-lived, but it is more than a protest vote: it has already exposed the fragility of Labour’s support. Ultimately, if Starmer cannot inspire at least some genuine enthusiasm, he risks becoming a one-term Prime Minister.
Talia Clements is a Intern at Bright Blue. The views expressed in this article do not necessarily reflect the views of Bright Blue.