The Maldives' departure from the Commonwealth is regrettable and disappointing, Boris Johnson said as he pledged to keep working with the troubled the nation.
When the Maldivian government announced its departure on Thursday it claimed the country had been "unfairly and unjustly" treated by the global body.
The Commonwealth was due to consider sanctions - including suspension - against the nation after its "lack of progress" on a raft of democratic reforms.
The Foreign Secretary said work had to be done to ensure the stability of the islands, which have been in political turmoil since its first democratically elected leader resigned four years ago.
"The UK is disappointed that the Maldives government has decided to withdraw from the Commonwealth," Mr Johnson said in a statement.
"We believe in the Commonwealth and its commitment to improving the lives of people across all its member states. The Commonwealth is an organisation dedicated to developing free and democratic societies, and to promoting peace and prosperity. And we regret that the Maldives has chosen to leave.
"We will continue to work with the Maldives government to help strengthen democracy, particularly freedom of speech and the media and independence of the judiciary.
"The stability of the country must be central to what happens next."
The Maldives' former president, Mohamed Nasheed, quit his post in 2012 and claims he was deposed at gunpoint.
The authorities in the Maldives have since been accused of a string of political and democratic violations.
The prime minister at the time, David Cameron, urged leaders at last year's biennial Commonwealth Heads of Government Meeting to toughen up their approach over the "unacceptable" actions of the nation's administration.
In its resignation statement the Maldives hit back, accusing the Commonwealth of trying to become an "active participant in the domestic political discourse" of the country and using it as an "easy object" to increase its global political standing.
Commonwealth secretary-general Baroness Scotland said she and the family of nations were saddened and disappointed by the decision but hoped the move would be only a "temporary separation".
She said: "The Commonwealth family at large - its member governments and its peoples worldwide - will share my sadness and disappointment at this decision.
"The Commonwealth Charter reflects the commitment of our member states to democracy and human rights, development and growth, and diversity.
"We will continue to champion these values and to support all member states, especially small and developing states, in upholding and advancing these practically for the enduring benefit of their citizens.
"Therefore, we hope that this will be a temporary separation and that Maldives will feel able to return to the Commonwealth family and all that it represents in due course."
The Commonwealth Ministerial Action Group, which deals with persistent and serious violators of the Commonwealth's shared principles, had been monitoring the Maldives' progress on reforms.
At its last meeting a few weeks ago, the group highlighted the lack of progress in areas like the prompt release of political leaders and misuse of anti-terrorism legislation.
It said that in the "absence of substantive progress across the priority areas" it would consider its options, including suspension from the Councils of the Commonwealth, at its next meeting in March.
In a statement the Maldives ministry of foreign affairs said: "The government of Maldives has decided today to leave the Commonwealth. The decision to leave the Commonwealth was difficult, but inevitable."
It added: "The Commonwealth has sought to take punitive actions against the Maldives since 2012 after the then president of Maldives resigned, and transfer of power took place as per the procedures set out in the constitution."
The statement said that since the change of leader the Commonwealth Ministerial Action Group and the Commonwealth Secretariat "have treated the Maldives unjustly and unfairly".
"The Commonwealth has sought to become an active participant in the domestic political discourse in the Maldives, which is contrary to the principles of the charters of the UN and the Commonwealth.
"The CMAG and the Commonwealth Secretariat seem to be convinced that the Maldives, because of the high and favourable reputation that the country enjoys internationally, and also perhaps because it is a small state that lacks material power, would be an easy object that can be used, especially in the name of democracy promotion, to increase the organisation's own relevance and leverage in international politics."