A Libyan government envoy, Mohammed Ismail, has been in London in the past few days for talks with the British authorities, the BBC has learnt.
The Foreign Office said that in all its contacts with Libyan officials, it had made it clear that "Gaddafi has to go".
News of the visit emerged after Libyan Foreign Minister Moussa Koussa flew to Britain and was said to have defected.
Meanwhile, the US says air attacks have destroyed about a quarter of the Libyan government's military's capabilities.
Following Mr Koussa's unexpected arrival in the UK on Wednesday, there were unconfirmed reports that other senior Libyans were defecting.
The pan-Arab TV channel Al-Jazeera said the intelligence minister, deputy foreign minister and General People's Congress speaker were awaiting flights in Tunisia.
Oil Minister Shukri Ghanim has denied any intention to leave Libya. Ali Abdul Salaam Treki, who was recently named as Libya's permanent representative to the United Nations, is not accepting the post.
A government spokesman told reporters that they were all in Libya, but that it was also possible that some had left the country on a mission.