Britain may lose its AAA credit rating after voting to leave the European Union (EU) in a national referendum on Thursday, Standard & Poors rating agency said Friday.

"We think that an AAA-rating is untenable under the circumstances," S&P chief ratings officer Moritz Kraemer told the Financial Times.

The markets reacted sharply to news that the UK is leaving the EU with the British pound plummeting to its lowest since 1985. The pound plunged 10 percent.

Stock markets from Tokyo to London collapsed on Friday following the vote.

The euro also dropped to 1.10 against the dollar as compared to 1.13 on Thursday.