Akmal Shaikh was arrested in north west China in 2007
The family of a Briton facing execution in China for drug smuggling claim he is mentally ill and are seeking clemency.
Akmal Shaikh, from north London, was arrested in September 2007 in Urumqi, north-west China, but denies knowledge of the 4kg of heroin he had with him.
His brother, Akbar, said he was praying China would recognise Shaikh's bipolar disorder and stay the execution.
The Foreign Office said it understood the case had been referred to China's Supreme People's Court for review.
British officials say they were "greatly concerned" after Shaikh's original appeal was turned down.
Legal charity Reprieve, which campaigns for fair trials and promotes human rights, fears a ruling - quickly followed by Shaikh's execution by shooting - to be imminent.
Akbar Shaikh said his brother, 51, who is married with three children, had struggled for years with his illness.
"We are all very worried for Akmal's safety as we know he is unable to defend himself properly. He will be extremely disorientated and distressed right now.
"We are praying that the Chinese courts will see that he is not of sound mind, and prevent his execution."
Reprieve said it gained approval for forensic psychologist Dr Peter Schaapveld to visit Shaikh but that he was denied access on arrival in China.
However, having spoken to Embassy staff who had been granted access and read statements from people who knew Shaikh, he said the evidence "clearly pointed" to a severe mental disorder.
"He thus should be as a matter of urgency assessed by a mental health professional and treated accordingly," he said.
The case is being supported by mental health charities Mind and Sane.
Reprieve claims Shaikh has always maintained he went to China to start a career as a pop star, despite no history of public singing, having previously lived in Poland where he tried to set up an airline.
It says he was duped into carrying a bag for someone who claimed to be able to give him work in a nightclub, only for police to find the heroin when he landed in China.
The charity's legal director Sally Rowen said: "For emotionally disturbed people like Akmal Shaikh, the experience of imprisonment can be highly traumatic.
"So imagine the disorientating, frightening effect of being imprisoned in a country where you cannot speak the language and barely understand what is happening to you."
The charity has called on Gordon Brown to intervene.
A Foreign Office spokesman said the prime minister had raised the case with China's leadership "several times".
"We understand that Chinese Ministry of Foreign Affairs announced on 13 October that the appeal has been denied and the case referred to the Supreme People's Court for review," said the spokesman.
"We are greatly concerned to hear that the death sentence has been maintained.
"We have already made representations to the Chinese authorities at the highest levels and representations continue in both China and London."
Consular officials last visited Shaikh on 8 September. They are working with Reprieve to ensure he has appropriate legal representation.