UK Foreign Secretary William Hague said the Syrian opposition was the people's "sole legitimate representative" and a "credible" alternative to the current regime of Bashar al-Assad.
On Tuesday, Hague told parliament the UK now recognizes the National Coalition of the Syrian Revolutionary and Opposition Forces, Syria's newly-formed umbrella opposition group, as the nation's legitimate government, the BBC reported.
The announcement follows similar moves by France, Turkey and six Gulf states and comes a day after recognition from the European Union, Reuters said.
The US has stopped short of fully recognizing the opposition while campaigning for an end to the crisis, according to the BBC.
Current estimates put the death toll for the 18-month conflict between 30,000- 35,000 people.
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"This step is very important and I think it will encourage more Syrians to join the coalition and trust it and it will also encourage other European states to recognize it," coalition spokesman Walid al-Bunni told Reuters.