Foreign Secretary William Hague has 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 on Sunday. "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.