Lawyers for Lindsay Sandiford, the woman from Redcar accused of smuggling £1.6 million of cocaine into Bali, have written to the British Embassy and Indonesian officials claiming she's being threatened in prison.
She could face the death penalty if convicted, after being arrested with an alleged 5kg of drugs at the city's airport in May.
In the letter, seen exclusively by ITV News, her legal team appeal for "special protection" for Mrs Sandiford. They ask she "be kept away from all threats and pressure", and ask for improvements to the conditions she's being held in.
Mrs Sandiford has been reported as saying she agreed to carry a package into Bali on behalf of a drugs gang, after they threatened to kill her son. The letter describes her as a "whistleblower", after she worked with police following her arrest. Her involvement in a sting operation led to the arrest of four suspected gang members, including three Brits.
A London-based pressure group that's working on her case is concerned for her safety.
Mrs Sandiford, a former legal secretary who lived in Redcar, as well as Cheltenham and India, is already being held in isolation at a police station in Bali after receiving threats. Her lawyers have also criticised conditions at the jail. Mrs Sandiford is a vegetarian, but her legal team says she's being denied a vegetarian diet.
But she could be moved to the city's notorious Kerobokan prison as her case progresses, and could be held for years while it's heard.
Her co-operation with police should count in her favour, but she could still face death by firing squad if convicted.
A Foreign Office spokesman said it took any reports of a British national being mistreated in a foreign prison very seriously, and raises such reports with local authorities.