Foreign Secretary William Hague tonight insisted it was "right" to let former Libyan intelligence chief Musa Kusa come to Britain despite anger at the idea of granting him asylum.
Mr Hague admitted there were "issues" over how to handle the defector, but stressed that Mr Kusa's decision to abandon Muammar Gaddafi had "weakened" the regime.
He also signalled that police would be allowed to interview Mr Kusa about Lockerbie and other historic crimes, saying: "We want more information about past events."
The comments came amid claims that Gaddafi's right-hand man was offered asylum in the UK as an enticement to leave Libya last week - raising the prospect of taxpayers footing a multimillion-pound security bill.
The Foreign Office refused to comment on the suggestion, saying only that Mr Kusa would be "entitled to apply for asylum".
But Tory MP Ben Wallace, parliamentary aide to Justice Secretary Ken Clarke, told the Mail on Sunday: "This man should not be granted asylum or any other special treatment. The only proper outcome is to bring him to justice.
"Britain needs to make up its mind quickly. There will be no shortage of courts that will readily seek his extradition.
"The last thing the UK wants is for Kusa to languish, at taxpayers' expense, in legal no-man's-land."
The potential for a "domino effect" from Mr Kusa's defection was highlighted this evening by reports that his deputy Abdulati al Obeidi has fled to Athens.
Mr Hague declined to say whether Mr Kusa had been contacting ex-colleagues urging them to follow his example.
But he mounted a robust defence of the decision to allow him into Britain, stressing that there had been "no deal" offering immunity.
"I think that when someone like that says they want to get out it would be quite wrong to say no, you have got to stay there," he told the BBC's Andrew Marr show.
"The Crown Office in Scotland want to talk to him about what has happened in the past, such as Lockerbie. My officials are discussing with the Crown Office tomorrow how to go about that.
"That is not a bad thing either. We want more information about past events."
Despite the rebels showing no sign of making headway against Gaddafi's better armed and trained forces, Mr Hague dismissed the prospect of ground troops being sent in.
And he indicated he did not believe that the conflict would end in a stalemate. "Let's be clear, if the Libyan regime tries to hang on in this situation, they are internationally isolated, they can't sell any oil," he said.
"There is no future for Libya on that basis, and so I think even the prospect of stalemate should encourage people in Tripoli to think, 'Well, Gaddafi has now got to go'."
The Foreign Office disclosed that a team led by experienced diplomat Christopher Prentice had arrived in Benghazi yesterday to forge links with the opposition.
The move follows the embarrassing episode last month when a UK group was briefly detained by rebels after turning up uninvited at dead of night in a helicopter.
"It will build on the work of the previous team and seek to establish further information about the Interim National Council, its aims and more broadly what is happening in Libya," a spokesman said.
Meanwhile, Archbishop Desmond Tutu - a long-term critic of Gaddafi - suggested it might be "the lesser of two evils" to offer the dictator immunity.
"I would say, as I have just said now, you keep having to balance what is a lesser evil," he told the BBC. "I feel that in the best of worlds, it would be the best thing to say that you clobber him, capture him and let him stand for trial.
"But we know that doesn't usually happen in the world in which we inhabit and say what is the lesser of two evils - to let him have a soft landing and save the lives of as many people as we possibly can."Reuse content