Britain is not making deals with envoys of the Libyan regime, Downing Street insisted today, as news emerged that UK officials held private talks with a senior aide of Muammar Gaddafi's son Saif over recent days.
It is understood that a meeting took place with Mohammed Ismail after he came to London to see family members and he was given a message to take back to the Gaddafi regime.
Prime Minister David Cameron's spokesman confirmed this morning that the UK authorities had been in contact with Libyan officials but insisted: "There are no deals."
The only message being passed on was that "the next steps need to be an end to violence and Gaddafi needs to go", said the spokesman, who declined to confirm details of the Ismail meeting.
UK diplomats continue to debrief high-profile defector Musa Kusa, Colonel Gaddafi's former intelligence chief and foreign minister who flew to Britain on Wednesday evening, declaring he was no longer willing to work for the Libyan dictator.
Meanwhile, the Pentagon announced that from Saturday US warplanes will no longer conduct air strikes on Libya, though they will be available if help is requested by the Nato commander. This leaves the UK, France and Canada to carry out aerial attacks on targets on the ground.
Defence Secretary Robert Gates also said the US would not be providing rebels with arms or training, telling a Congressional committee: "My view would be, if there is going to be that kind of assistance to the opposition, there are plenty of sources for it other than the US."
Mr Kusa was being questioned today at a "secure location" in the UK. Mr Cameron's spokesman did not say whether he has yet provided any useful information about the state of Col Gaddafi's regime or its military struggle with rebel troops, which today seemed to be drifting towards stalemate.
"Discussions with officials are continuing but I am not able to go into details," said the spokesman.
Asked about the reported Ismail visit, he replied: "We have been very clear over the past few weeks that we have been having contact with Libyan officials but we have not been providing commentary on that and we are not going to start now.
"The one thing I would say about contacts we are having with people is we are sending them all one very clear message which is that Gaddafi must go.
"Our very clear position throughout has been that the next steps need to be an end to violence and Gaddafi needs to go."
Mr Cameron yesterday urged Col Gaddafi's "henchmen" to follow the example of his former foreign minister and defect. Mr Kusa's flight to the UK exposed the "desperation and the fear right at the very top of the crumbling and rotten Gaddafi regime", he said.
But this morning his spokesman denied suggestions that promises of immunity from prosecution were being offered in the hope of encouraging further defections.
Reports today suggested the UK had been in touch with as many as 12 senior regime figures to try to persuade them to abandon Col Gaddafi.
"There are no deals," said the spokesman. "There is a very clear position which is that if people are in the UK, they are subject to UK law."
Mr Cameron said yesterday that the Government would offer every assistance to Scottish prosecutors who have asked to interview Mr Kusa about the 1988 bombing of Pan Am flight 103 over Lockerbie, which killed 270 people.
It was not clear whether he was being sought as a suspect in the planning of the atrocity, which took place when he was a senior officer in Col Gaddafi's feared intelligence agency, or as someone certain to hold vital information because of his former position.
Pressure was growing on the Government to hand over Mr Kusa to police for questioning on Lockerbie and on the murder of Pc Yvonne Fletcher, shot outside the Libyan People's Bureau in London in 1984.
Pamela Dix, from Woking, Surrey, whose brother Peter was killed in the Lockerbie bombing, urged the Government to comply with the Scottish Crown Office request.
"I would be very keen to see him being questioned," said Ms Dix. "He may have material information and evidence and I would wish to see every opportunity used to see if that is the case.
"I hope that David Cameron sticks by his commitment that there will be no diplomatic immunity."
But former Labour foreign minister and UN diplomat Lord Malloch-Brown said it was "critically important" that Kusa is seen to have been "well-received" in the UK because it would encourage others to follow him.
Lord Malloch-Brown told the BBC Radio 4 Today programme: "We have to have a strategy now of trying to fragment the regime by peeling people away from it and if we locked him up, that would deter that."
Despite a second high-profile defection yesterday, of former foreign minister Ali Abdessalam Treki, Col Gaddafi insisted he would not step down.
As his forces regained momentum against the Libyan rebels, he accused the Nato leaders of being "affected by power madness", adding: "The solution for this problem is that they resign immediately and their peoples find alternatives to them."
Calls were made this morning for ministers to update Parliament on the contact with Mr Kusa and Mr Ismail.
Senior Tory MP Edward Leigh told the House of Commons: "Clearly we have embarked on what was to be a humanitarian mission and we are now very heavily engaged in the murky politics of Libya. What is going on? The House would like to know."
Mr Cameron said today that the mission was "difficult and dangerous" for British forces but insisted the UK should be proud of its role.
Speaking in Swansea, during a Welsh Assembly election campaign event for the Conservatives, the Prime Minister said: "I know the operations they are involved in are difficult and dangerous. I know that what we are undertaking is difficult.
"But I think we should be clear that by acting rapidly with our allies, with France, with America, we have prevented a massacre in Benghazi of innocent people and we stopped a deadly dictator in his tracks.
"We should be proud that we in Britain helped to lead that action."
Labour's former defence secretary Lord Robertson, secretary-general of Nato from 1999 to 2003, today warned that European ground troops might be needed to finish off the Gaddafi regime and provide stability in the wake of the dictator's departure.
In a House of Lords debate, Lord Robertson asked: "If the attrition goes on and civilians can't be saved just from the air, are we simply going to stand back if troops on the ground could be decisive?
"And if we took that route, whose boots would be on the ground? Even in the best-case scenario of a stabilisation force on the ground in post-conflict Libya, whose boots would make up that force?
"The boots assuredly would not be American. Their President and Defence Secretary have made it very clear this week their people are tired of coming the rescue of a Europe that won't invest in its own security insurance.
"Europe had better wake up to the historic challenge it faces at this historic moment."
But former defence chiefs warned of the dangers of "mission creep".
Lord West of Spithead, a former chief of the Royal Navy, said: "If there were any move towards the use of land forces, I believe we should immediately leave the coalition.
"Mission creep as regards the UN resolution to regime change is very dangerous. I think we need to go back to the UN and ask them if they want regime change."
And Lord Craig of Radley, chief of defence staff at the time of the first Gulf War, said that "loose talk of arming the rebels" smacked of "mission creep".
"Are we not very close to being accused of involvement and taking sides in a Libyan civil war?" he asked.
Air Chief Marshal Lord Stirrup, who was head of the armed forces until last year, said that ousting Gaddafi had to be the UK's "political objective".
"Our military intervention can only end with his removal," he said.
But this goal would have to be achieved by non-military means, as it was "unlikely in the extreme" that the rebels would be able to take Tripoli by force, even if armed from outside.
Lord Stirrup warned that the UK was "spreading our Armed Forces very thin".
"They will do what is asked of them but, for all their 'can do' attitude, they are a finite resource, ever more finite by the month," he said.
Having committed our forces, he said, "we must see the endeavour to a successful conclusion, placing the very highest degree of urgency for finding a political resolution to this crisis as soon as possible".
Scottish First Minister Alex Salmond made clear that police want to talk to Mr Kusa "on the basis of information that might be provided" and that there was no suggestion at this stage that he was being treated as a suspect.
Mr Salmond told Sky News: "Nonetheless, there is every reason to believe that this individual can shed light on the Lockerbie atrocity and the circumstances that led up to it.
"There's a whole range of information and documentation that the Scottish Prosecution Service and our judicial process have assembled, and there's certainly every indication that he would be an important person to interview in terms of determining what the next judicial stage might be."
He added: "Obviously it is right and proper that the coalition forces acting under the auspices of the United Nations will want to encourage defections from the Gaddafi regime. That seems to be a perfectly proper thing to do.
"However, remember also that the UN made it clear in the case of atrocities within Libya that nobody would be immune from prosecution, that people would be brought to book and held to account for any crimes they committed against civilians in Libya.
"Surely that must be the case in terms of the wider ramifications of previous international terrorist incidents. So my strong advice to the UK authorities - and I've no reason to believe this won't be the case - is to allow the facility to the Crown Prosecution Service in Scotland and the police to interview Musa Kusa as soon as possible."