Gordon Brown and other senior British politicians have angrily condemned China for executing a British man said to have had mental problems. Akmal Shaikh, 53, was killed early this morning by lethal injection after being convicted of drug smuggling.

Despite frantic appeals by the Foreign Office for clemency, Shaikh was executed at 10.30am local time (2.30am British time) in Urumqi. Campaigners believe he is the first European in 58 years put to death in China.

Shaikh, a father of three from Kentish Town, north London, was found with 4kg of heroin in his suitcase in September 2007. His supporters say he had suffered a breakdown, was delusional and was tricked into carrying the drugs.

Britain is not planning any retaliation beyond criticism. The Chinese ambassador to London, Fu Ying, was summoned to the Foreign Office to hear first-hand the government's anger. The Foreign Office minister Ivan Lewis was to protest about the execution and the Chinese government's decision to cancel an annual meeting between the two countries, scheduled for January in Beijing, where they were due to discuss China's human rights record.

Lewis said: "China cannot expect to receive the respect they yearn from the international community until they abide by minimum standards of human rights. Engagement with China is non-negotiable and any alternative strategy is simply not credible. But by being so clear in our public criticism of China's handling of this case we are demonstrating that it is not business as usual."

British ministers have been struck by the apparent near-universal support for the execution within China. David Miliband, the foreign secretary, writing on his blog, said: "We have said many times we welcome the economic rise of China and believe its integration into the world system is one of the great opportunities of the 21st century, not just one of the challenges. Events like those of today will only fuel the argument of those who say this is an impossible dream and that the value systems are just too different.

"I don't believe that. But it is a reminder of how different can be our perspective. We need to understand China (and the massive public support for the execution). They need to understand us."

Shaikh learned only yesterday that he would be killed today. He was informed by two cousins who had flown to China seeking a reprieve.

"We are deeply saddened, stunned and disappointed at the news of the execution of our beloved cousin Akmal," said Soohail and Nasir Shaikh in a statement.

The two men said they were "astonished" that the Chinese authorities refused to investigate their cousin's mental health on the grounds that the defendant ought to 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, especially when this was apparently bipolar disorder, in which we understand the sufferer has a distorted view of the world, including his own condition."

Amid an angry exchange of words between London and Beijing, the British prime minister 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. At this time our thoughts are with Mr Shaikh's family and friends and I send them our sincere condolences."

Brown had raised the case on several occasions, including during a meeting with the Chinese premier, Wen Jiabao, at the Copenhagen summit and in a personal message in the past few days.

While British ministers have been careful not to promise any retaliation against the Chinese government, their statements demonstrate their anger at what they regard as Beijing's refusal to recognise Shaikh's basic human rights.

In Beijing the Chinese government said it resisted any interference in its judicial affairs. "We express strong dissatisfaction and opposition to the British reaction," said Jiang Yu, a foreign ministry spokeswoman. "We hope the British side will face this case squarely and not put new obstacles in the way of relations between Britain and China."

Chinese judges and lawyers receive instructions from the Communist party on their handling of political cases, but Jiang claimed the country's courts were independent. "China judicial independence brooks no interference." China treated citizens of all nations as equals in dealing with drug-related crime, said Jiang.

The Chinese embassy in London insisted "Shaikh's rights and interests were properly respected and guaranteed" and disputed British claims about his condition. "The concerns of the British side were duly noted and taken into consideration by the Chinese judicial authorities.

"Out of humanitarian consideration visas were granted to the two cousins of Mr Shaikh on Boxing Day and they were given access to meeting Mr Shaikh in China. As for his possible mental illness which has been much talked about, there apparently has been no previous medical record."

China executes three times as many people as the rest of the world's official executions put together – at least 1,718 in 2008 according to Amnesty International, although the real figure is likely to be much higher.

China has assured British officials that they have gone further than they do with other countries' prisoners to give advance warning of the execution, around three or four days, and allow the family access. Shaikh's cousins were allowed to see him for an hour and a half.

One senior figure closely involved with the case said China's reluctance to give ground was because many of those executed by the state were likely to have mental health problems and that Shaikh was "the tip of the iceberg".

Britain believes China is keen to move on from this case quickly but senior figures say it will inevitably colour dealings between the two countries for some time.

Sally Rowen, the legal director of the human rights group Reprieve, said: "The death of Akmal Shaikh is a sad indictment of today's world, and particularly of China's legal system. ... We at Reprieve are sickened by what we have seen during our work on this case."

Lewis told Radio 4's Today programme this morning: "It's a deeply depressing day for anyone with a modicum of compassion or commitment to justice in Britain and throughout the world."

He said it was "reprehensible" and "entirely unacceptable" that the execution had gone ahead without any medical assessment. "This execution makes me personally feel sick to the stomach but I'm not going to make idle threats.

"This morning is not the time for a kneejerk reaction. It's true we must continue to engage with China but it needs to be clear as that country plays a greater role in the world they have to understand their responsibility to adhere to the most basic standards of human rights. China will only be fully respected when and if they make the choice to join the human rights mainstream and incidents like this do not help the international community's respect or relationship with China."

Lewis said that there had been 27 ministerial representations to China about Shaikh's case in the last two years. Despite the increased international dialogue with China "all of those representations have been in vain and this is a very very different view of what constitutes universal human rights".

"Clearly Mr Shaikh has mental health problems. And whilst we differ with China anyway on the issue of the death penalty ... the biggest single issue here that causes us so much consternation is that they refused to even do a medical assessment knowing that there was evidence of mental health problems; that is what is unacceptable.

"In the context of a working relationship, a constructive positive relationship ... we expect our partners to behave differently and behave better."

Chinese media have yet to report the execution, but the state-run news agency Xinhua carried a statement by the supreme court defending its judgment. "The evidence was certain and the facts were clear," it said.

The court defended its decision to refuse UK requests for a mental examination. "There is no reason to cast doubt on Akmal Shaikh's mental status," it said.

Legal activists disputed the assertion that the government could not intervene in the court system. "China's judiciary is not independent, it is totally controlled by the government," said the civil rights lawyer Teng Biao.

"This case shows the hardline stance of the government. China now can ignore pressure from international society and won't compromise even a little on the issue of human rights."

Shaikh's lawyer for the supreme court review, Zhang Qingsong, said he was not allowed to meet his client.

Following vocal British criticism of China's stalling tactics at the Copenhagen climate conference this month, the rhetorical relations between the two nations have arguably hit a low not seen since the Tiananmen Square massacre in 1989. But experts said the long-term impact would be small.

"The two sides are just posturing for their own citizens," said Wu Qiang of Tsinghua University. "Akmal Shaikh is only an isolated case. Unless the UK raises the issue to the EU level I don't think there will be big influence on relations."

The execution delighted China's nationalists. Online comment was overwhelmingingly favourable.

"Well done! The man deserves the death sentence. China has finally shown it can be tough in front of foreigners," noted a post under a TV clip about the news.

On the website ifeng.com, Chahu18 wrote: "I can't believe the British government condemned this action ... Do they support drug smuggling? Britons, you think it is still 1840 when you could use opium to harm Chinese people? I am with Chinese government this time!"

Reprieve said it had medical evidence that Shaikh believed he was going to China in 2007 to record a hit single that would usher in world peace. It said he was duped into carrying a suitcase packed with heroin on a flight from Tajikistan to Urumqi.

Reprieve said the last European to be executed in China was an Italian, Antonio Riva, who was shot by a firing squad in 1951, along with a Japanese man, Ruichi Yamaguchi, after being convicted of involvement in what China alleged was an American plot to assassinate Mao Zedong and other high-ranking Communist officials.

Shaikh's family thanked Brown, Miliband and other British ministers for their efforts and asked the media for "space to grieve".