UK Prime Minister Sir Keir Starmer has declared that Britain will not join the United States and Israel in offensive strikes against Iran, saying he will not commit UK troops to actions that lack a clear legal foundation.
“I will not commit our military personnel to unlawful action. That is not what they would expect and deserve. They are entitled to better than that,” Starmer said, drawing a distinction between Britain’s approach and that of Washington.
The prime minister said the UK’s decision not to join the initial US-Israeli strikes was “deliberate”, stressing that his government “does not believe in regime change from the skies.”
“This government does not believe in regime change from the skies,” he told MPs. “We will not join offensive action now.”
Starmer invoked the legacy of the Iraq war in defending his stance. “We all remember the mistakes of Iraq, and we have learned those lessons. Any UK actions must always have a lawful basis and a viable, thought-through plan,” he said.
While refusing offensive involvement, Starmer made clear that Britain shares concerns about Iran’s nuclear ambitions. “It is clear the Iranian regime must never be allowed to get its hands on nuclear weapons,” he said.
The prime minister also urged British nationals in the region to register their presence with authorities to ensure support can be provided if needed, and to monitor regularly updated Home Office travel advice.
However, Starmer confirmed that the United States had requested permission to use British bases to stop Iranian missiles “at source” — targeting weapons in storage depots or at launch sites before they can be fired.
He said he accepted the request “in order to prevent Iran firing missiles across the region” and killing civilians. The government insists this support amounts to defensive action and is lawful under international rules as “collective self-defence.”
Starmer stressed repeatedly that the UK is not joining the US and Israel’s offensive strikes.
He noted that France and Germany are also prepared to allow US activity from their bases aimed at degrading Iran’s missile-firing capability.
The move has exposed divisions in Parliament. The opposition Conservative Party and several MPs argue Britain should have taken part in the initial strikes. Others — including some within Starmer’s own Labour Party — have voiced concern about any involvement that could draw the UK deeper into the conflict.
Meanwhile, US President Donald Trump defended the decision to launch military action, calling it the “last, best chance” to stop Iran’s regime.
Speaking at the White House for the first time since the strikes, Trump said US forces are continuing “large-scale combat operations.” The joint US-Israeli attack reportedly killed Iran’s Supreme Leader, Ali Khamenei, and Israeli forces have since launched fresh strikes on Tehran.
Despite the escalation, the US defence secretary has said there will not be an “endless war.”
Starmer’s position reflects a balancing act: supporting allies in defensive measures while drawing a firm line against direct participation in what he characterises as unlawful offensive military action.