David Cameron insisted today that the Government was doing everything it could to get hundreds of British nationals out of Libya as the country descended further into violence and bloodshed.
Fears were growing for up to 170 UK oil workers stranded in remote and highly vulnerable desert locations across the North African state.
The latest charter plane evacuating dozens of Britons from the capital, Tripoli, left for Gatwick at 4.30pm, carrying 79 passengers including 34 Britons.
Another charter flight will depart from Tripoli tomorrow, which the Foreign Office said was likely to be the last.
The Foreign Office believes up to 500 UK nationals could still be in the country in total. The Prime Minister urged them to "leave now".
The security situation around Tripoli has been deteriorating as fighting between supporters and opponents of dictator Colonel Muammar Gaddafi has escalated.
Mr Cameron said there would be more flights made available as necessary and that a second Royal Navy ship, HMS York, was being deployed to the area.
HMS Cumberland, which left second city Benghazi with 68 Britons yesterday, is set to return after docking tonight in Malta. Its voyage has been delayed by poor conditions at sea.
Those Britons who have returned to the UK today brought with them tales of ever-deepening chaos and of the terror of being stranded in oilfield camps threatened by roaming militias.
After heavy criticism that the Government's response to the crisis has been slow and shambolic, Mr Cameron chaired emergency planning meetings with senior ministers and security advisors this morning.
"We will do everything we can today and tomorrow to help those people and planning is under way to do just that," the Prime Minister said.
He added: "I would say that people do need to leave now and that is the message that 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."
SAS troops are understood to be ready to move in to evacuate those stuck in the oilfields, although the Ministry of Defence refuses to comment on the movements of Special Forces.
One oil worker who was left isolated in the remote area of Ghani but had a lucky escape home told of the panic as rumours swept their compound that a militia was on its way.
Richard Foscolo, of Barry, South Wales, said security staff had deserted, leaving them without arms.
"As time progressed the situation became more and more worrying. We had heard about looting in a nearby oilfield in Amal and there was concern we could be next," he said.
"On Monday, we received reports that a militia known as the Black Shadow were coming to attack the compound.
"It sparked absolute chaos, with Libyans draining fuel tanks to try and make sure they had enough petrol to drive off into the desert."
He managed to get to Tripoli after a plane was diverted to the oilfield he was at.
Labour leader Ed Miliband said there was "a worrying whiff of incompetence" about the Government's handling of the situation.
"Frankly, I think Mr Cameron has got to get a grip on the way this Government works," he said.
"Clearly the Government should have acted earlier to make flights available so that people could come home.
"Now they have just got to move as quickly as possible and get as many flights out there as possible so that British citizens who obviously want to come home, and want to get out of the situation they find themselves in Libya, can come back to the UK."
As violence continued to mount in Libya, Mr Cameron warned the Gaddafi regime that it would be held to account by international law.
Britain is pushing at the United Nations for sanctions and investigations into alleged crimes against humanity.
"The message is very clear - that the violence we have seen is appalling and unacceptable," the Prime Minister said.
"I have this very clear message for people in that regime, this warning for people in that regime - the world is watching you and the world will hold you to account.
"Britain, through the United Nations, is pressing for asset seizures, for travel bans, for sanctions, for all of the things that we can do to hold those people to account, including investigating for potential crimes against humanity, or war crimes, or crimes against their people.
"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."
Asked whether military force would be considered, the Prime Minister said: "We will do what is necessary to keep people safe and we will do what is necessary to bring our people back.
"People in that regime should recognise that the world is watching what they do and they have a very clear warning that through the United Nations, Britain and others will be pushing for the asset seizures, for the travel bans and for work in terms of investigating crimes which may have been committed, that could be committed, to make sure no-one is beyond the reach of international law."Reuse content