The UK has agreed to a US request to use British military bases for “defensive” strikes on Iranian missile sites, Sir Keir Starmer has said.

But the prime minister said the UK had learned lessons from the “mistakes of Iraq”, and was not involved in the initial strikes on Iran and “will not join offensive action now”.

Sir Keir said the basis of the decision to accept the US request was the “collective self-defence” of allies and protecting British lives, accusing Iran of pursuing a “scorched-earth strategy”.

The BBC understands the US is likely to use RAF Fairford in Gloucestershire and Diego Garcia in the Indian Ocean for strikes on Iranian missile sites.

In his video statement on Sunday, Sir Keir said the US would use UK bases for the “specific and limited defensive purpose” of destroying Iran’s missiles “at source”.

He added that the move was in accordance with international law, and the UK government had published what it said was a summary of its legal advice.