The home secretary, Yvette Cooper, is under mounting pressure to airlift a group of more than 60 Tamil asylum seekersfrom a remote Indian Ocean island to the UK. The Tamils, a mix of single adults and children who are part of family units, have been stranded on Diego Garcia, part of the British Indian Ocean Territory (BIOT), since October 2021. They had fled persecution in Sri Lanka and were travelling in a fishing boat hoping to reach Canada to claim asylum. But their boat developed a leak and they were rescued by the Royal Navy who took them to Diego Garcia, where there is a US military base, for what they thought would be a few days. But almost three years later they remain there, with their fate uncertain. A letter detailing a mass suicide attempt involving 22 people was written by Paul Candler, the commissioner for BIOT, who works out of the Foreign, Commonwealth and Development Office (FCDO) in London. Tessa Gregory, a partner at law firm Leigh Day, representing some of the Tamils, said: “The camp is in crisis. Sadly, news of the mass suicide attempt and self-harm is not surprising to those who are aware of the conditions there. “This is a group of extremely vulnerable individuals who fled their country seeking only safety and freedom. It is imperative that the foreign secretary and home secretary act now to end this cruelty and bring all of those on Diego Garcia to the UK without delay.” Sulaiha Ali, of Duncan Lewis Solicitors, representing others in the group of Tamils, said a “complete crisis” is now unfolding in Diego Garcia “We hope that a decision to bring all the migrants to the UK is now made without further delay,” she said. “The decision now seems to rest with the home secretary. These desperate men, women and children plead with her to make that decision expeditiously.” Lawyers in the UK have mounted a legal challenge, claiming they are being unlawfully detained on the island, held in a fenced-in area the size of a football pitch. It is guarded by G4S officers, and there is limited access to areas beyond the fence. The case is due to be heard in September. At a hearing on Friday, the acting judge of the BIOT supreme court, Margaret Obi, granted the asylum seekers extended bail to allow them to access more parts of the island. She said: “The situation appears to be deteriorating rapidly.” The Tamils are reported to be living in rat-infested tents, with self-harm said to be rife, and amid claims of child sexual abuse. On Thursday Candler sent a letter to the Foreign Office minister Stephen Doughty outlining the deepening crisis on the island. He had initially requested that some, but not all, of the Tamils be urgently brought to the UK. Theforeign secretary, David Lammy, wrote to the home secretary on 16 July asking her to grant permission. But as the situation on the island worsened after the mass suicide attempt by 22 Tamil men not part of family units, he sent another letter asking for everyone – 64 people in total – to be brought to the UK. He warned Doughty of the risk of arson, riots and hunger strikes with the possibility of widespread disorder among those not in the initial group earmarked to be brought to the UK, as well as the reputational risk for the UK and Diego Garcia if action is not taken. He urged Doughty to pursue his request urgently for all the Tamils on Diego Garcia to be brought to the UK with home office ministers. But there has not yet been a response to this request from the Home Office. The FCDO has been approached for comment after the Home Office referred the Guardian to them.