"Time is of the essence" in the struggle to prevent Libyan leader Col Muammar Gaddafi "brutalising" any more of his people, Prime Minister David Cameron has told MPs.
In a Commons statement on 14 March 2011, Mr Cameron said that there should be "no let up on the pressure we put on this regime".
He said the UK was urgently working on a draft UN security council resolution, which would authorise the operation of a no-fly zone over Libya.
The prime minister also told MPs that the UK was calling on the security council to approve "much tougher measures against mercenaries" fighting against the Libyan uprising.
He argued that the spread of democracy in North Africa and the Middle East was in the UK's national interest.
The PM warned that Libya could become a "failed pariah state", threatening Britain's security.
If the "legitimate aspirations" of Libyan rebels were "crushed", it would send a "dreadful signal" to others in the region striving for political change, he added.
Labour leader Ed Miliband said the situation in Libya was "grave and pressing".
He called on the government to "translate the no-fly zone phrase into a practical plan".
Separately in his statement, Mr Cameron said that "the thoughts of everyone in this House, indeed everyone in our country, are with the Japanese people" following Friday's earthquake and tsunami.
"We stand with you at this time," he said.
Mr Miliband said: "The tragedy that has hit the country is of almost unimaginable horror and scale, as all of us who will have seen the pictures on our television screens over the weekend would have felt."