Libya unrest: UK reaction to UN vote in quotes
UK forces are preparing to help enforce a no-fly zone over Libya after the UN backed "all necessary measures", short of an invasion, to protect civilians from Col Muammar Gaddafi's forces.
The timetable for possible British military engagement is not yet known.
Here is how some British politicians and diplomats have been reacting to the developments:
Foreign Secretary William Hague
"We have said all along that Gaddafi must go, that the Libyan people must be able to have a more representative government and determine their own future. And is it necessary to take these measures to avoid greater bloodshed, to try to stop what is happening in terms of the attacks on civilians, on the people of Libya.
"We have said for a long time that there should be three criteria for being able to take action under this kind of authorisation - a demonstrable need, and the actions and statements of the Gaddafi regime in recent days have provided that demonstrable need; secondly, a clear legal basis, this is the clear legal basis in a resolution of the United Nations Security Council; and third, broad support from within the region itself, and that is evident in the statement of the Arab League and the readiness to participate in a no-fly zone.
"As of tonight, those three criteria are satisfied and fulfilled. And this places a responsibility on members of the United Nations, and that is a responsibility to which the United Kingdom will now respond."
British ambassador to the UN, Sir Mark Lyall Grant
Sir Mark said Libya's Col Gaddafi had launched air strikes "in anticipation of what we expect to be a brutal attack using air, land and sea forces" on Benghazi.
"He has publicly promised no mercy and no pity".
The UK government welcomed the fact that the UN had acted "swiftly and comprehensively in response to the appalling situation in Libya", he said.
"We, along with partners in the Arab world and in Nato, are now ready to shoulder our responsibilities in implementing Resolution 1973."
Shadow foreign secretary Douglas Alexander
"I pay tribute to the work that Britain and other nations have undertaken to ensure that the Security Council has reached this important agreement.
"The responsibility for this crisis rests squarely with the Gaddafi regime and by this resolution the United Nations has now placed a responsibility on its members to act to protect the Libyan people."
Former Liberal Democrat leader Sir Menzies Campbell
"This resolution has been a long time coming but it has enormous political weight and legitimacy because of the regional support for it from the Arab League.
"Gaddafi threatens a bloodbath of his own people.
"The duty under international law to protect the Libyans from him is paramount."
Stop the War Coalition
Anti-war activists said the Prime Minister had been "itching" to bomb Libya, accusing him of not learning the lessons of the "disastrous" wars in Iraq and Afghanistan.
A spokesman for the Stop The War Coalition said: "Air attacks on Libya will not help end the civil war but will escalate it and could be the prelude to a much wider war.
"History shows us that the consequences of Western intervention are almost always disastrous and not in the interests of those it claims to support."
Chairman of UK-based Libya Watch, Mohammed Abdel Malek
"I am very delighted, very delighted indeed [that the resolution has been passed] - for my sake, for the sake of the Libyan people, for the sake of the British and the Americans and the French who supported this resolution and made it possible.
"And I think that the West can be rest assured that they did the right moral thing."
Former Defence Secretary Michael Portillo
"Contingency planning [by UK forces] will mean of course moving the assets to a position where they can be used, making sure the aircraft have been moved forward.
"And it will also mean identifying targets. Because if you're just going to enforce a no-fly zone, that means you've got to fly your aircraft over Libyan territory to make sure no Libyan aircraft are flying over the territory.
"And that means that you run the risk of being engaged by anti-aircraft assets belonging to Gaddafi, and that means that you have to be prepared to take those out, or indeed you might take the view that you weren't prepared to fly your aircraft at all until you had taken that risk away from your pilots."
Tony Benn, veteran Labour politician and Stop the War Coalition president
"The question is, is it right for us to start a new war? We've got the Afghan war, to start a war in Libya, because the language used covers up what it's really about, it's an attempt to get rid of Gaddafi.
"Without holding any cards for Gaddafi, and I'm not supporting him, the fact is that the revolution in Libya has not led to the victory that it did in Tunisia and Egypt, and therefore we would be entering into a civil war.
"And the truth is you're going into a war without clear objectives, although everybody knows what the British objectives and American objectives are.
"I think this is going to damage the popular movement in the Middle East by allowing it to be presented as a western intervention."
Shashank Joshi, associate fellow at the Royal United Services Institute
The UN security council resolution which authorises member states to employ "all necessary measures" to protect civilians has "a great possibility of being effective."
"This will limit Gaddafi's ability to affect grave damage on civilians as long as it's not just a no-fly zone but also the ability to target his forces on the ground.
"If he pushes further east he knows his forces on the ground will be at the risk of being bombed."
The former First Sea Lord and Home Office Minister Lord West
"We should really be ready to take action almost immediately. That's the way the military works, there'll have been a lot of options discussed.
"I do believe we ought to have some Arab air forces involved in this. I think it's amazing that we've got this phrasing in there 'All necessary measures to protect civilians' which does allow strikes.
"They're much easier than maintaining a tenuous no-fly zone."
Crossbench peer and former Foreign Secretary Lord Owen
Lord Owen said he feared the UN resolution was too late, and that action must now be taken immediately.
"Gaddafi's forces are very near to Benghazi and there is a real danger that he will push on... and he will try and get in as close as he can with his forces before we can even possibly consider striking.
"I think that we have to consider very carefully, and I hope it's already been done by military planners, what is the best course to halt Gaddafi before Benghazi.
"That is the crucial thing. That is protecting the most civilians, so that we do not have an urban fight, which we all know is very expensive of civilian life."