British Prime Minister David Cameron and French president Nicolas Sarkozy yesterday issued a joint statement supporting the interim National Transitional Council.
The statement came as a Downing Street spokesman confirmed diplomats were on the ground in Libya and had made contact with the council.
He also made it clear that the UK government would oppose a proposal to allow Muammar Gaddafi to leave the country to live in exile and avoid trial for human rights abuses as part of a deal to end the civil war.
The move was put forward by Italy, which, until pro-democracy protests broke out, had been one of the Gaddafi regime`s closest allies.
A Turkish proposal at the London conference aims to broker a ceasefire between the two sides; until Sunday night, Ankara had blocked NATO from taking command of military operations.
Cameron appeared to dismiss the Turkish suggestion yesterday, in response to a call by former Liberal Democrat leader Sir Menzies Campbell.
He urged the Prime Minister to "do all in his power to prevent the endorsement of any proposals which would enable Colonel Gaddafi to regenerate the apparatus of terror and repression, which has sustained him for too long".
Cameron replied, "It is important that, while there are such clear and flagrant breaches of the (United Nations Security Council] resolution going on, we should do everything we can to protect people and actually, as a result, that is actually driving back the Gaddafi regime".
The London conference, hosted by Foreign Secretary William Hague, will include representatives of 40 countries and international organisations, including UN Secretary General Ban Ki-moon, African Union chairman Dr Jean Ping, Qatari Prime Minister, foreign ministers from Iraq, Jordan, United Arab Emirates, and Morocco, US Secretary of State Hillary Clinton, and foreign ministers from across Europe.
The Arab League, Lebanon and Tunisia will also be represented.
Russia will not be represented, as its leaders have protested at what they see as an abandonment of the UN resolution in favour of a move towards formal regime change.
Russia`s suspicions appeared to be confirmed by the conference agenda.
Although the summit will consider what should happen next and how international aid can be better taken into Libya, it will principally look at rebuilding the country after the war.
The statement by Cameron and Sarkozy suggested regime change was now the main aim, even though officially the Prime Minister said it was to protect the Libyan population from human rights abuses.
The statement noted the Gaddafi regime "has completely lost its legitimacy", while transition could include the "Interim National Transitional Council, the pioneering role of which we recognise, the civil society leaders as well as all those prepared to join the process of transition to democracy".