Unease as Cameron reveals 'troops out' date

Mr Cameron said UK forces will not stay beyond 2015 in a combat role but the withdrawal would be "conditions based".

The policy was immediately attacked by Shadow Foreign Secretary David Miliband who accused the Government of sending out "mixed messages" – a point echoed by senior Tory Andrew Tyrie.

Mr Cameron said the date was "safe" because the coalition forces planned to hand over to Afghan forces by 2014, "based on the conditions on the ground".

At least two MPs within his party were, however, unhappy at the announcement.

Julian Lewis said setting a date for withdrawal put pressure on the Afghan government, not the Taliban while Mr Tyrie said: "I certainly think there's a danger of mixed messages.

"Do we have a fixed timetable or do we have a policy based on conditionality? I was also left a little unclear about what exactly we're leaving behind after 2015.

"There's certainly a risk that if we are locked into a timetable, we could empower the Taliban."

The former head of the Army, Gen Sir Mike Jackson, also raised concerns, saying he was "wary" about setting dates, and a plan to transfer power "does not equal reality".

Mr Cameron also faced accusations he was being "pushed into concessions" over the release of Lockerbie bomber Abdelbaset al-Megrahi, an issue that has dominated his first visit to Washington as Prime Minister.

His plans were changed so he could meet senators from New York and New Jersey, where many of the bombing victims came from.

Downing Street initially ruled out any talks but then said they had "found time in the diary".

Mr Cameron also agreed to review the papers in the case – but resisted demands for a new inquiry. He said it was simply "good manners" that he had altered his schedule to meet senators and it was "reasonable" to have asked Cabinet Secretary Sir Gus O'Donnell to review paperwork to see if there was any more information that could be released.

He denied Britain's position as "junior partner" in the special relationship meant he could be pushed around by the US on issues like Lockerbie.

"I'm not being pushed into any concessions by anybody," he said.

The ongoing pressure from the US about the release of Megrahi saw Scotland's First Minister write to US senators last night.

In a letter to John Kerry, chairman of the Senate Committee on Foreign Relations, Alex Salmond made clear the Scottish government made the decision to free Abdelbaset al-Megrahi on compassionate grounds and had received no representations from BP on the matter. The First Minister said the decision was made with "integrity" and following a "clear legal process".

Libyan Megrahi is the only man to have been convicted of the Lockerbie atrocity which killed 270 people in the bombing of Pan Am flight 103 on December 21, 1988.

He was released from a Scottish prison last August with cancer, having been given three months to live, but is still alive.

Mr Salmond said he had written the letter making clear the Scottish Government's stance to assist the committee with a proposed hearing on July 29.

After acknowledging "the terrible pain and suffering inflicted on the victims and the relatives of all those who died in the Lockerbie atrocity", he rubbished claims the Scottish administration were lobbied by oil giant BP to release the Libyan.

"My understanding is that the recent interest from the committee and from other senators stems mainly from concerns over any role played by BP in Megrahi's release," he said.

"I can say unequivocally that the Scottish government has never, at any point, received any representations from BP in relation to Megrahi."

Mr Salmond has previously criticised ex-premier Tony Blair for negotiating a prisoner transfer agreement (PTA) with Libya in 2007 – which was not invoked for Megrahi's release – at the same time as sealing a deal for BP in the country, saying it gave rise to suspicions of "deals in the desert".