Nasheed's lawyer Hasan Latheef said the Maldivian Democratic Party (MDP) leader had sought political asylum and was granted political refugee status.
A prominent human rights campaigner and Maldives' first democratically elected president, 49-year-old Nasheed had been allowed to go to Britain in January for a spinal cord surgery following a deal brokered by Sri Lanka, India and the UK.
"President (Abdulla) Yameen has jailed every opposition leader and cracked down on anyone who dares to oppose or criticise him," Nasheed said in a statement proclaiming his refugee status.
The Maldives government said yesterday that it was disappointed that the UK had agreed to "be part of this charade", adding that British ministers were helping with efforts to circumvent the law.
More From This Section
Nasheed became Maldives' first democratically elected leader in 2008, ending three decades of rule by former strongman Maumoon Abdul Gayoom, and served for four years before he was toppled in what he called a coup backed by the military and police.
Nasheed was jailed for 13 years on terrorism charges after being accused of illegally ordering the arrest of a judge in a trial that put a spotlight on instability in the Maldives.
The jail term was widely criticised by international bodies, including the United Nations, and foreign governments.
A popular figure on the world stage, Nasheed's case was championed with the help of a international legal team that included Amal Clooney, the British human rights lawyer and wife of the American actor Georg Clooney.
Cameron described Nasheed as his "best friend" in 2011 and this year hosted the ex-president, his wife and Amal at Downing Street after he arrived in London.
The Maldives stripped Nasheed of his pension entitlements and health insurance last month, after demanding he return from medical leave in Britain.