Akmal Shaikh was arrested in north west China in 2007
The rights of a Briton facing execution in China next week for drug smuggling have been respected, the Chinese say.
The Chinese foreign ministry said the "grave crime" had been handled in accordance with the law.
The UK has "intensified" pleas for clemency for Akmal Shaikh, 51, of north London, who has denied knowledge of the 4kg of heroin found with him in 2007.
His family says he has mental health problems, but China's Supreme People's Court denied his appeal.
Mr Shaikh, who was arrested in September 2007 in Urumqi, north-west China, faces execution on 29 December.
A Chinese foreign ministry spokeswoman said: "China's judicial authorities independently handled this case in accordance with the law. Drug smuggling is a grave crime in international practice.
"During the entire process, the litigation rights and the relevant rights and interests of the defendant were fully respected and guaranteed."
Legal charity Reprieve says Mr Shaikh suffers from bipolar disorder and is mentally ill.
He would become the first EU national to be executed in China in 50 years.
The Foreign Office said the government was "alarmed and deeply concerned" at the news, and it would "renew and intensify" appeals to the Chinese for clemency.
It "deeply regrets" that mental health concerns had no bearing on the final judgment turning down his appeal, and ministers and the prime minister were "closely engaged", it said.
Reprieve, which campaigns for fair trials and promotes human rights, called on Gordon Brown to intervene and "speak directly" to the Chinese president.
Reprieve's director, Clive Stafford Smith, said: "We very much hope that Akmal Shaikh does not become a victim of the regrettably cold political climate that has resulted [from Copenhagen].
"The prime minister should speak directly with President Hu, emphasise that Chinese compassion would be viewed as a great favour to the British people, and note the consistent view of Chinese and British doctors that a full mental health assessment is vital to assess how Akmal's illness contributed to the offence."
Mr Shaikh's family were "begging" the Chinese authorities to show compassion and consider his mental health problems, he added.
Reprieve said Dr Peter Schaapveld, a forensic psychologist, believes it was very likely that Mr Shaikh's strange behaviour was "influenced or caused by" his mental illness.
It said Chinese experts have joined Dr Schaapveld in calling for a proper mental health evaluation.
The charity claims Mr 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.