The political crisis engulfing Downing Street deepened this afternoon as a co-ordinated cabinet rebellion threatened to dismantle Sir Keir Starmer’s authority. Senior ministers, speaking on condition of anonymity, confirmed that at least six cabinet members have presented the Prime Minister with a joint ultimatum: either abandon the flagship “New Deal for Britain” policy or face an unprecedented confidence vote.

The revolt, orchestrated by figures close to the Labour right, marks the most serious challenge to Starmer’s leadership since he took office. It centres on the New Deal’s centrepiece: a sweeping overhaul of workers’ rights and national energy policy, which critics within the cabinet argue is “electorally toxic” and risks alienating centrist voters. “This is not a fringe rebellion,” said Dr Eleanor Shaw, professor of political science at the London School of Economics. “The weight of the mutineers suggests a systemic failure of starmerite management.”

Number 10 initially attempted to downplay the unrest. A Downing Street spokesperson described the meeting as “frank and constructive”. Yet the language of unity evaporated within hours, as the BBC obtained a leaked letter signed by the six rebels, including a prominent cabinet minister. The letter warns that “continued adherence to an unelectable agenda will consign Labour to opposition for a generation”.

The timing could not be more precarious. Starmer faces a crucial Commons vote on the New Deal next week, with Labour’s internal division threatening to hand the government a damaging defeat. Rebel sources indicated they would whip against the bill if Starmer refused to compromise. “This is about survival,” one senior backbencher told The British Wire. “Starmer must choose between his ideology and his job.”

Inside the cabinet room, the atmosphere has been described as “poisonous”. Several ministers have refused to attend official photo-ops. The Chancellor, a key ally of Starmer, has privately pleaded for calm, but his interventions have been met with scorn. “He has zero credibility,” a junior minister said. “He backed the policy until the polls turned sour.”

The rebellion echoes the chaotic final months of Theresa May’s premiership, when cabinet resignations brought down her authority. “Starmer is in a similar death spiral,” noted Sir Anthony Seldon, historian and former vice-chancellor. “Once the cabinet openly rebels, the prime minister is a lame duck. The only question is how long the ending takes.”

Publicly, Starmer remains defiant. In a statement this evening, he said: “I will not be swayed by threats or ultimatums. Labour was elected to deliver change, not to manage decline.” But behind the scenes, aides are preparing contingency plans. A leadership challenge could be triggered if 40 Labour MPs sign a letter of no confidence. Sources say the threshold may be reached by the weekend.

The crisis also exposes deeper fractures in the Labour coalition. The soft left, which forms Starmer’s core support, is furious at the rebels’ audacity. “They are sabotaging the biggest reform programme in decades,” said a party strategist. Meanwhile, the unions have rallied behind Starmer, warning that any dilution of the New Deal would trigger a “war with our movement”.

Financial markets registered unease. Sterling fell 0.8 per cent against the dollar amid fears of political instability. “Investors hate uncertainty,” said Ruth Miller, macroeconomist at Capital Economics. “A leadership crisis just as the government faces economic headwinds is a recipe for volatility.”

As the parliamentary lobby briefed journalists, the mood was grim. “This is not a storm in a teacup,” a former shadow minister said. “The ship is taking on water and the captain is arguing with the crew.” The next 48 hours will determine whether Starmer can patch the hull or whether the mutineers seize the wheel.

One potential compromise involves delaying the New Deal’s most contentious elements, such as scrapping zero-hours contracts. But rebels have demanded a complete U-turn. “Half-measures won’t save him,” said Professor Shaw. “The rebels want a scalp. They want Starmer to eat his own words.”

The Conservative Party, watching from the sidelines, has begun weaponising the chaos. A Conservative Party spokesman said: “Starmer is weak, divided and out of touch. Labour cannot govern itself, let alone the country.”

Whether Starmer can survive remains unclear. A YouGov snap poll, due tomorrow morning, is expected to show Labour sliding further. For now, Number 10 is a fortress under siege. “He might weather this,” one insider admitted. “But the walls have cracks you can drive a cabinet minister through.”