Britain has threatened to raid the Ecuadorian embassy in London if WikiLeaks founder Julian Assange is not handed over, Ecuador's foreign minister says.

At a media conference in Quito, Ricardo Patino said the position taken by the British government was "unacceptable".

"Today we've received a threat by the United Kingdom, a clear and written threat that they could storm our embassy in London if Ecuador refuses to hand in Julian Assange," he said.

"We are not a British colony."

WikiLeaks later weighed in, saying any threat to the embassy's sanctity was a "shameful act".

In its letter, the British government mentioned an existing law that gives Britain the power to strip an embassy of its status.

Ecuador says it wants to give the Australian asylum, but the British government is refusing to provide him with safe passage, meaning he will be arrested as soon as he leaves the Ecuadorian embassy to where he fled several months ago.

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Mr Patino said a decision on the WikiLeaks founder's asylum request would be made public late tonight.

In response to Mr Patino's press conference, the British Foreign Office said it was "determined" to extradite Mr Assange to Sweden.

"The UK has a legal obligation to extradite Mr Assange to Sweden to face questioning over allegations of sexual offences and we remain determined to fulfil this obligation," said a Foreign Office spokesman.

The Diplomatic and Consular Premises Act of 1987 appears to give the British foreign secretary, William Hague, the right unilaterally to revoke the diplomatic status of consular premises.

But British government officials have made clear that this was very unlikely to happen.

While a diplomat in Quito did remind the Ecuadorians of the obscure law, British officials say it was designed to encourage a decision rather than threaten imminent action.

Sorry, this video has expired 'There are limits' to Assange support: Roxon ( Radio National )

'Extraordinary threat'

Mr Assange is trying to avoid extradition to Sweden, where he is wanted for questioning over sexual assault allegations made by two WikiLeaks supporters in 2010.

The Australian activist says he had consensual sex with the women.

Mr Assange, who enraged Washington in 2010 when his WikiLeaks website published thousands of secret US diplomatic cables, says he fears he could be sent to the US, where he believes his life would be at risk.

In the past he has appealed for the Australian Government to intervene, but Attorney-General Nicola Roxon this morning told Radio National there was little Australia could do.

"We've certainly made diplomatic contact and we've obviously been providing consular support as well, but ultimately, I think you and your listeners would understand that this is a matter between Mr Assange and Ecuador," she said.

"Increasingly it seems it's a matter between Ecuador and the UK."

WikiLeaks issued a statement about the UK government threat, saying any "transgression against the sanctity of the embassy is a unilateral and shameful act".

"WikiLeaks condemns in the strongest possible terms the UK's resort to intimidation," it said.

"A threat of this nature is a hostile and extreme act which is not proportionate to the circumstances and an unprecedented assault on the rights of asylum seekers worldwide."

Without precedent

Sorry, this video has expired Law expert says Ecuador granting asylum a symbolic gesture only

Don Rothwell, professor of international law at the ANU, agreed the threat to raid the embassy, if true, was without precedent.

"I'm not aware of any precedent in relation to this type of matter, and at face value it seems to be a fairly extraordinary threat that the British government is making against the government of Ecuador," he told ABC News Breakfast.

"It clearly indicates how serious the UK is taking the Assange matter.

"Assange is in breach of his bail conditions under UK law. And quite rightly the UK has said that if he steps outside the embassy he would be re-arrested."

But Professor Rothwell says even if Ecuador grants Mr Assange asylum it will only be symbolic, and he is still likely to eventually be extradited to Sweden.

"Because any capacity for Assange to leave the UK given the current position of the UK government would seem to be exceptionally remote," he said.

"I think that irrespective of the position adopted by Ecuador, whatever sort of asylum arrangement that might be put in place is either going to be symbolic or it's going to be very temporary. We'll likely to see Mr Assange facing extradition to Sweden in the very near future."

Mr Assange has not been charged with any offence in Sweden or in the US.

ABC/Reuters