The cost of a round-the-clock guard outside the Ecuadorean embassy in London, where Julian Assange took refuge last June, has reached almost £3m, the Metropolitan Police have said.
Scotland Yard estimated costs of £2.3m in pay that would have covered normal duties, and £600,000 on overtime.
The Wikileaks website founder faces extradition to Sweden over sexual assault allegations, which he denies.
Mr Assange, 41, fears onward extradition to the US.
He believes he could face charges there over the release of top secret documents by Wikileaks, whose publication of a mass of leaked diplomatic cables has embarrassed a number of countries.
Sweden wants to question him over allegations that he sexually assaulted two female ex-Wikileaks supporters while he was in Stockholm to give a lecture in 2010.
Mr Assange entered the embassy, in Knightsbridge, after the UK's Supreme Court dismissed his bid to reopen his appeal against extradition. It had given him a two-week grace period before extradition proceedings could start.
He has been warned he will be arrested when he leaves the embassy for breaking the terms of his bail conditions, necessitating the 24-hour guard by Metropolitan Police officers.
An embassy spokesman said: "The Ecuadorean government is concerned by the significant cost to the taxpayers of London of policing the embassy at the present time.
"However, we believe this expenditure could be avoided if the UK government would provide the undertakings that the Ecuadorean government has sought that there will be no onward extradition of Julian Assange to the United States.
"The Home Office has the power to offer such an assurance but has so far declined to do so. Until we obtain these undertakings, the Ecuadorean government will continue to protect Julian Assange's human rights that are enshrined in international law."
The UK government has said it has a legal obligation to hand over Mr Assange to Sweden, but that its extradition laws include human rights safeguards.
It has also pointed out that the UK and Sweden would both need to agree to any attempt to send Assange on to the US.