Officers have been stationed outside ever since the WikiLeaks founder jumped bail and fled there on June 19 after losing his battle in the British courts against extradition to Sweden, where he faces questioning over allegations of rape and sexual assault. Ecuador has granted him political asylum.
Scotland Yard police headquarters estimated the total cost to the end of January at £2.9 million ($4.5 million) - £2.3 million in salary for the officers stationed on duty and the rest in overtime payments.
The embassy is a flat in a mansion block in west London's plush Knightsbridge district. It is across the street from the back of Harrods department store.
Assange, a 41-year-old Australian former computer hacker, founded the WikiLeaks anti-secrecy website which enraged Washington by releasing cables and war logs relating to the wars in Iraq and Afghanistan in the biggest security breach in American history.
A spokesman at the Ecuadoran embassy said: "The Ecuadoran government is concerned by the significant cost to the taxpayers of London of policing the embassy".
"However, we believe this expenditure could be avoided if the UK government would provide the undertakings that the Ecuadoran government has sought that there will be no onward extradition of Julian Assange to the United States."
"The Home Office (Britain's interior ministry) has the power to offer such an assurance but has so far declined to do so."
"Until we obtain these undertakings, the Ecuadoran government will continue to protect Julian Assange's human rights that are enshrined in international law."