Britain has recognised the Libyan rebel council as that country’s "sole governmental authority" and has expelled the Gaddafi-regime’s diplomats, the BBC reports.
Instead the UK will ask the rebel National Transitional Council to appoint a new diplomatic envoy.
The British move follows those of the US and France. The UK had previously said it recognised "countries not governments", but Foreign Secretary William Hague said this was a "unique situation."
Mr Hague said:
"I'm making this announcement today to reflect the facts on the ground and to increase support for those fighting and working for a better future in Libya.”
"What I have announced today will allow us to give further assistance to the people of Libya and underline the message to the Gaddafi regime that their legitimacy has come to an end."
The change meant the UK could give the rebels "greater practical assistance than we've been able to give so far", he added.
For the main opposition Labour party, shadow foreign office minister Stephen Twigg told the BBC:
"We agree that the National Transitional Council is best able to represent the people of Libya, so it makes sense to recognise them, I hope other countries will also recognise them, and it's time for Gaddafi's diplomats to leave London."