Kyaw Zwar Minn said staff were asked to leave the building by Myanmar’s military attaché, and he was dismissed as the country’s representative.
British Foreign Secretary Dominic Raab has condemned the “bullying actions,” but the UK has accepted the change.
Myanmar’s military seized power in a coup on 1 February, sparking protests and escalating violence.
Kyaw Zwar Minn has criticized the military coup, and called for Myanmar’s ousted leader Aung San Suu Kyi to be released.
About 600 people – including dozens of children – have been killed so far as pro-democracy protesters demand a return to power of elected leader Ms Suu Kyi and her National League for Democracy (NLD) party.
Through a spokesman out the front of the embassy on Thursday morning, Kyaw Zwar Minn urged the UK government not to recognize the military junta’s newly appointed ambassador, and to send them back to Myanmar.
“There was a coup in Myanmar in February. Now there is the same situation in central London,” he said, adding embassy staff were being threatened with “severe punishment if they don’t continue to work for the military general”.Police were reportedly called to stop staff re-entering the building. Protesters gathered outside after news spread that the ambassador had been locked out.
According to the Vienna Convention on diplomatic relations, an ambassador’s job officially ends once the host country has been informed. The Foreign Office confirmed it received the notification, and that it “must accept the decision taken by the Myanmar Government”.