US Navy F-18E Super Hornets, which have been used to strike Isis targets in Syria. It is not known what planes British pilots have used to carry out strikes.
The prime minister’s spokeswoman said on Friday that up to a dozen pilots had been involved since September, but they were not operating under a British chain of command. “The PM was aware that UK personnel were involved in US operations and what they were doing.”
She said it was a long-standing practice for the UK to embed forces with other countries and this was no different. But she was not able to point immediately to any written or oral statement setting out that British air crew were involved in bombing missions in Syria.
Details of British personnel’s involvement in strikes by allied nations’ forces were revealed by a freedom of information request by the pressure group Reprieve.
The House of Commons voted against military action in Syria in 2013, although at that time the targets envisaged were President Bashar al-Assad’s military forces. Parliamentary authorisation has only been given for UK air strikes against Isis in neighbouring Iraq.
Cameron and the defence secretary, Michael Fallon, made clear they were considering extending the military air campaign to Syria after the Tunisian beach massacre on 26 June, in which 30 Britons were among the 38 people killed. The pair have indicated that they would seek MPs’ approval for an extension of air strikes into Syria, but no vote is expected before autumn.
On Thursday the defence minister Lord Howe issued a lengthy written statement setting out the scale of British military operations in Syria and Iraq, making reference to UK air-to-air refuelling and reconnaissance over Syria, and the number of bombing raids in Iraq. It made no reference to British pilots dropping bombs in Syria.
The Speaker, John Bercow, is certain to grant an urgent statement to MPs requiring ministers to explain whether they have misled the house, or acted in breach of a parliamentary resolution.
The prime minister’s spokeswoman said the British aircrew were acting within international law and were merely carrying duties as part of an exchange with allies. She said it was well-known that the UK was in the lead as one of the anti-Isis coalition forces.
British forces had been embedded with their French counterparts on military operations since the 1950s, she said, and it was a way of retaining close military alliances, as well as provide valuable experience.
She declined to reveal whether Labour’s interim leader, Harriet Harman, had been told of the Syrian involvement when she was briefed by Cameron and defence chiefs on Tuesday at a specially convened meeting of the national security council.
The government is waiting for Labour to elect a new leader before appealing to the party to support open British involvement in bombing raids in Syria. The new leader is likely to accede to the request, but there is bound to be anger within Labour about whether Cameron should have been more open about the existing involvement.