Foreign Secretary Margaret Beckett has urged the leader of a "wholly unconstitutional" military coup in Fiji to restore democracy.
The South Pacific nation faces suspension from the Commonwealth after Commodore Frank Bainimarama declared Prime Minister Laisenia Qarase had been dismissed.
Britain is halting military co-operation with Fiji and has put contingency plans in place to protect the ex-patriate community should the security situation worsen.
Condemning the coup, Mrs Beckett said it was "a major setback to the process of democracy in Fiji".
"It has damaged Fiji's economy, international reputation, as well as its relations with the international community," she said.
"These actions are wholly unconstitutional: the military should not have become involved in the political process.
"I strongly urge Commander Bainimarama to return Fiji to democracy as quickly as possible.
"As a result of this action, the UK is taking steps to suspend immediately bilateral military assistance to Fiji and is considering further measures with both EU and Commonwealth partners.
"We are in close contact with the British community in Fiji and have contingency plans in place should the security situation deteriorate."
Britain has no troops in Fiji and the Ministry of Defence indicated that it had been engaged in a "very, very modest programme of defence assistance".
