A spokeswoman of the Foreign Office said the Chinese ambassador to the UK Fu Ying has been 'summoned,' adding that Britain reiterated to her its condemnation of the execution of Akmal Shaikh, who suffered a bipolar disorder.
The diplomatic action came after Brown said he was 'appalled' and 'disappointed' that China ignored repeated appeals to show mercy on Shaikh, a 53-year-old father of three, for drug smuggling.
The execution by lethal injection took place despite repeated calls from his family and the British government for leniency, citing his mental state, saying that he suffered from bipolar disorder.
Ambassador Fu Ying was summoned after the execution sparked condemnation from the UK government. In a statement, Brown said, "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. I am particularly concerned that no mental health assessment was undertaken."
Foreign Office Minister Ivan Lewis, who held last-ditch talks with the Chinese ambassador in London on Monday, said UK had made 27 representations to China in two years, and believed it had done everything it possibly could.
Foreign Office Minister Ivan Levis said the execution made him 'sick to the stomach.'
A spokeswoman for the Chinese Foreign Ministry, Jiang Yu, told a press briefing in Beijing that no-one had the right to comment on China's judicial sovereignty.
"We express our strong dissatisfaction and opposition to the British government's unreasonable criticism of the case. We urge (them) to correct their mistake in order to avoid harming China-UK relations," she said.
Shaikh is the first European Union national to be executed in China in more than 50 years. In its statement, China said Shaikh was convicted of 'serious' drug trafficking.
"The amount of heroin he brought into China was 4,030g, enough to cause 26,800 deaths, threatening numerous families," it said.
Leading campaign group, The Reprieve, has condemned the execution of Akmal Shaikh. The organisation said it was 'horrified' that no mercy was shown to 53-year-old Akmal Shaikh.
Sally Rowen, the group's legal director, said it was a 'barbaric' act against a man with mental health problems. Reprieve had taken up Shaikh's case for the family.
Katherine O'Shea, Reprieve's communications director, said it was 'devastated' that Shaikh had been killed.
"This guy was a very vulnerable person, extremely ill. He slipped through the cracks of society, and was frankly failed by China and by their legal system. And it's an absolute disgrace that he should have been killed," she said.
Akmal Shaikh's brothers Suhail and Nasir, who travelled to China to visit their cousin in prison and make a last-minute plea for clemency, said they were 'deeply saddened, stunned and disappointed' by the execution.
They said, "We are astonished at suggestions that Akmal himself should have provided evidence of his own fragile state of mind. We find it ludicrous that any mentally-ill person should be expected to provide this."
His daughter Leilla Horsnell said, "I am shocked and disappointed that the execution went ahead with no regards to my dad's mental health problems, and I struggle to understand how this is justice."
Shaikh's family said he had been delusional and duped into a carrying a suitcase that did not belong to him when he was found with 4kg of heroin in Urumqi, north-west China, in September 2007.
His daughter said drug smugglers in Poland convinced him they would make him a pop-star in China. Charity MDF, The Bipolar Organisation, described the execution as 'medieval rough justice' and an 'absolute tragedy.'
Spokesman Robert Westhead said, "The way the Chinese authorities have stubbornly failed to take account of this poor man's severe mental illness shows that China is still stuck in the dark ages."
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