British prime minister Gordon Brown said he was "appalled" after China on Tuesday executed a British citizen caught smuggling heroin, dismissing pleas from the prisoner's family that he was mentally unsound.
Akmal Shaikh's relatives and the British government had appealed for clemency, arguing the former businessman suffered from bipolar disorder, also called manic depression.
The Chinese supreme court rejected the appeal saying they was insufficient grounds, and the Chinese foreign ministry said Shaikh had been given all due legal rights.
Brown condemned the execution in strong words that may raise diplomatic temperatures over the case.
"I condemn the execution of Akmal Shaikh in the strongest terms, and am appalled and disappointed that our persistent requests for clemency have not been granted," he said in a statement issued by the British Foreign Office.
"I am particularly concerned that no mental health assessment was undertaken."
China had yet to publicly confirm Shaikh had been executed in the western city of Urumqi, capital of Xinjiang region, at the time Brown made the statement. In London, a British Foreign Office spokesman said Britain had been informed by Chinese authorities of Shaikh's execution.
He would be the first European citizen to be executed in China since 1951, Western rights groups say.
Shaikh was still "hopeful" when relatives met him in Urumqi this weekend, his cousin Soohail Shaikh told reporters at Beijing airport late on Monday night.
"We beg the Chinese authorities for mercy and clemency to help reunite the heartbroken family," Soohail Shaikh had said.
Brown last week asked China not to execute Shaikh, who was born in Pakistan and moved to Britain as a boy.
The case could harden public opinion in Britain against China. It could also rile Chinese public opinion, resentful over what Beijing often calls "interference" in the country's internal affairs.
The two countries recently traded accusations over the troubled Copenhagen climate change negotiations.
Heroin use is a major problem in Xinjiang, which borders Central Asia. The region was convulsed by ethnic violence and protests in July, with further protests in September after widespread panic over alleged syringe attacks.
All executions in the city have used lethal injections in recent years, an official surnamed Jia told reporters at the detention center in Urumqi where Shaikh had been held.
Shaikh's defenders, including British rights group Reprieve which lobbies against the death penalty, say he was tricked into smuggling the heroin by a gang who promised to make him a pop star. Arrested in 2007, a Chinese court rejected his final appeal on December 21.
Reprieve posted on the Internet a recording Shaikh made of a song, "Come Little Rabbit", which it described as "dreadful", but which Shaikh believed would be an international hit and help bring about world peace.
"This is not about how much we hate the drug trade. Britain as well as China are completely committed to take it on," the British foreign secretary, David Miliband, said in a statement emailed to reporters. "The issue is whether Mr Shaikh has become an additional victim of it."
