Britain will not allow Wikileaks founder Julian Assange safe passage out of the country and will continue to seek to extradite him to Sweden, Foreign Secretary William Hague said on Thursday after Ecuador granted Assange political asylum.

"Under our law, with Assange having exhausted all options of appeal, the British authorities are under a binding obligation to extradite him to Sweden. We must carry out that obligation and, of course, we fully intend to do so," the foreign secretary said at a press conference.

"We will not allow Assange safe passage out of the UK, nor is there any legal basis for us to do so," Hague said, arguing that Britain is not a party to any legal instruments which require it to recognize the grant of diplomatic asylum by a foreign embassy in the country.

"We will remain fully committed to seeking a legal and binding bilateral solution to this with the government of Ecuador," he added.

The British Foreign Office expressed disappointment after Ecuador announced its decision to grant Assange political asylum earlier on Thursday.

Ecuadorian Foreign Minister Ricardo Patino said the country believed Assange's fears of receiving unfair trial and eventually being extradited to the United States are legitimate.

Hague said Britain does not accept the principle of diplomatic asylum and has "painstakingly explained the extensive human rights safeguards built into our law."

"It is important to understand that this is not about Assange's activities at Wikileaks or the attitude of the United States of America. He is wanted in Sweden to answer allegations of serious sexual offences," Hague said, adding that diplomatic asylum "should not be used for the purposes of escaping the regular processes of the courts."

Britain's Supreme Court dismissed Assange's appeal on May 30, paving the way for his extradition to Sweden over alleged sex crimes. Assange took refuge at the Ecuadorian embassy since June 19 to avoid extradition.

The 41-year-old Australian who founded the Wikileaks website has embarrassed several governments, including the United States authorities, by publishing millions of secret diplomatic cables on the internet.

Since his arrest in Britain in December 2010, Assange fought a lengthy legal battle against extradition, fearing that his return to Sweden would lead eventually to his extradition to the United States to face the anger of the authorities over his publishing of the diplomatic cables.