William Hague has insisted the British government would not allow Julian Assange safe passage out of the United Kingdom.
Hague said it was a "matter of regret" that the Ecuadorian government decided to grant the Wikileaks founder political asylum but warned that it "does not change the fundamentals" of the case.
Speaking at the Foreign and Commonwealth Office, he also warned that the case could go on for some "considerable" time.
Hague said: "We will not allow Assange safe passage out of the United Kingdom, nor is there any legal basis for us to do so."
“Under our law, with Mr 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 Ecuadorian Government's decision this afternoon does not change that in any way. Nor does it change the current circumstances in any way. We remain committed to a diplomatic solution that allows us to carry out our obligations as a nation under the Extradition Act.
“It is important to understand that this is not about Mr 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.
The UK "does not accept the principle of diplomatic asylum" Mr Hague said.
"It is far from a universally accepted concept: the United Kingdom is not a party to any legal instruments which require us to recognise the grant of diplomatic asylum by a foreign embassy in this country."
“Ecuador has expressed its concerns about the human rights of Mr Assange and sought guarantees from us in that area regarding his extradition to Sweden and indeed about any onward extradition and we have painstakingly explained the extensive human rights safeguards built into our law.
“No-one, least of all the Government of Ecuador, should be in any doubt that we are determined to carry out our legal obligation to see Mr Assange extradited to Sweden.
"He faces serious charges in a country with the highest standards of law and where his rights are guaranteed. We believe that should be assurance enough for Ecuador and any supporters of Mr Assange."