( CNN ) -- The British government condemned China 's execution of a British national Tuesday on drug smuggling charges . `` I ... am appalled and disappointed that our persistent requests for clemency have not been granted , '' Prime Minister Gordon Brown said . `` I am particularly concerned that no mental health assessment was undertaken . '' Akmal Shaikh was convicted of carrying up to 4 kilograms ( 8.8 pounds ) of heroin at the Urumqi Airport in September 2007 . According to Chinese law , 50 grams ( 1.76 ounces ) is the threshold for the death penalty . China defended the execution in a statement issued by the Chinese Embassy in London . `` Drug trafficking is a grave crime worldwide , '' the statement said . `` The concerns of the British side have been duly noted and taken into consideration by the Chinese judicial authorities in the legal process , and Mr. Shaikh 's rights and interests under Chinese law are properly respected and guaranteed . '' The 53-year-old is the first European executed in China in 50 years , according to the British legal group Reprieve . `` We are deeply saddened , stunned and disappointed at the news of the execution of our beloved cousin , Akmal , '' Soohail and Nasir Shaikh said in a statement issued on behalf of the family . `` This was carried out this morning despite repeated requests for clemency and a proper appraisal of Akmal 's mental state . '' His family and the British government had asked Chinese leaders for clemency . His supporters argued that Shaikh was mentally ill , and that Chinese officials did not take his mental condition into account when trying him . Shaikh 's advocates say he suffered from a bipolar disorder and that he was tricked into carrying heroin into China with promises of a career as a pop singer . Brown raised Shaikh 's case with Chinese Premier Wen Jiabao during the international climate summit in Denmark earlier this month . British Foreign Secretary David Miliband echoed Gordon 's concerns about the execution . `` The UK is completely opposed to the use of the death penalty in all circumstances , '' Miliband said . `` However , I also deeply regret the fact that our specific concerns about the individual in this case were not taken into consideration . ... These included mental health issues , and inadequate professional interpretation during the trial . '' Sally Rowen , legal director with Reprieve , condemned the execution . `` The death of Akmal Shaikh is a sad indictment of today 's world , and particularly of China 's legal system , '' she said . `` Akmal was a gentle man who suffered from a tormenting illness ... and was betrayed and deliberately killed by one of the most powerful nations on Earth . '' Before the execution , Philip Alston , the U.N. special rapporteur on extrajudicial executions , said it would be a `` major step backwards for China '' to execute a mentally ill man . `` Both Chinese and international law clearly indicate that a person who committed a crime while suffering from significant mental illness should not be subjected to the death penalty , '' Alston said in a statement released by Reprieve . China expressed hope that the case would not affect the relationship between the two nations . `` We value the China-British relationship , '' said Jiang Yu , a Chinese Foreign Ministry spokeswoman . `` So we hope the British authority can treat this matter rationally and not let it create new barrier between the two countries . I have emphasized that this is an independent criminal case . It has nothing to do with anything else . ''
NEW : China defended the execution in a statement issued by the Chinese Embassy in London . Akmal Shaikh 's supporters said he was mentally ill and officials did not take that into account when trying him . British government had asked China not to execute Shaikh but China says it has followed law .