Sir Keir Starmer has told MPs that the government "does not believe in regime change from the skies", putting him at odds with President Trump over the joint US-Israeli strikes on Iran.
In his first statement to Parliament since the strikes, Sir Keir defended his decision not to permit the use of UK bases for the initial wave of attacks.
"President Trump has expressed his disagreement with our decision not to get involved in the initial strikes, but it is my duty to judge what is in Britain's national interest," he told MPs.
However, the situation changed on Sunday when Iran's "outrageous" response became "a threat to our people, our interests and our allies", the PM said.
Iran's retaliation to the US and Israeli attacks had threatened British people across the Middle East, prompting the decision to allow the bases to be used to hit Tehran's missile infrastructure, he said.
