Evacuation plan stepped up as threat of further violence grows

Britain is drawing up emergency plans to rescue hundreds of Britons from Libya amid fears that Muammar Gaddafi's desperate attempts to cling on to power could lead to worsening chaos and bloodshed.

David Cameron, whose Government has been accused of incompetence and delay in its response to the crisis, promised yesterday it would do "everything it can" to remove stranded UK nationals.

He was speaking after the deteriorating situation was discussed at a two-hour meeting of ministers and defence and intelligence chiefs in Whitehall. They agreed to deploy military force if necessary to protect Britons trapped in Tripoli, the Libyan capital, or oil workers in desert sites, although sources made clear there was no question of troops being used to confront Colonel Gaddafi'.

SAS forces are on standby to be flown into Libya, while the RAF could be used to send food and water to Britons running low on supplies. Mr Cameron said: "We will do what is necessary to keep people safe and we will do what is necessary to bring our people back."

The most likely rescue option is to organise international convoys to reach Westerners in remote locations. A second Royal Navy ship, HMS York, is being dispatched to the region and more flights could be sent to Libya.

Ministers are anxious to remove as many Britons as possible from country over the weekend because of alarm that the Libyan dictator could escalate his brutal tactics. About 600 of the estimated 1,000 UK nationals working in the country have left since fighting broke out, with a few more escaping via a catamaran that docked in Malta yesterday.

Yesterday evening the Foreign Secretary, William Hague, called for all remaining Britons to make their way to Tripoli airport "at first light," saying: "Given that there are now only a small number left, the last Government-sponsored chartered plane will leave Tripoli tomorrow."

After days of bitter criticism, Mr Cameron flew back from a four-day tour of the Gulf States to take charge of efforts to reach the remaining stranded Britons. He said: "People do need to leave now and that is the message I give very strongly to British citizens in Libya. For those in the desert, we will do everything we can and we are active on that right now to help get you out."

The Foreign Office said security at Tripoli airport had been "deteriorating in recent hours and the route to the airport is becoming more precarious".

Mr Cameron sought to put pressure on Col Gaddafi and his acolytes by warning that their assets abroad could be frozen, that they could banned from travelling overseas and prosecuted for war crimes. He said: "People working for this regime should remember that international justice has a long reach and a long memory and they will be held to account for what they do."

The coalition Government has endured its most torrid week in power since Libya erupted in violence. Mr Cameron faced embarrassment when it emerged that he was accompanied by senior executives from defence contractors on his Gulf tour, while the Foreign Secretary, William Hague, looked on powerless as early attempts to organise rescue missions to Libya foundered. Nick Clegg, who had to cut short a skiing holiday to Switzerland to attend yesterday's meeting of the National Security Council, faced criticism over an ill-judged joke that he "forgot" he was in charge of Britain in Mr Cameron's absence.

Douglas Alexander, the shadow Foreign Secretary, said: "After the false starts earlier in the week, people will want continued assurance that the Government has now got a grip of the situation. In the next 24 hours, Government needs to focus on doing everything it can to help British nationals get out of Libya."