Britain and China were yesterday engaged in a fierce diplomatic argument after the Chinese government executed a UK citizen for drug trafficking, in spite of claims he was mentally ill and unfit to stand trial.

In an act that was roundly condemned by Gordon Brown, Britain's prime minister, China executed Akmal Shaikh, a 53-year-old father of three, who was caught smuggling heroin into China.

Britain had long argued there were strong signs Mr Shaikh suffered from a mental condition and that this should have prompted an act of clemency.

Mr Brown said he condemned the execution “in the strongest terms” and was “particularly concerned that no mental health assessment was undertaken”.

The UK foreign office underscored its anger by formally summoning the Chinese ambassador in London to the foreign office for a confrontation with Ivan Lewis, one of its ministers.

Mr Lewis told the ambassador in a “difficult conversation” that China had “failed in its basic human rights responsibilities.”

British officials privately indicated that they were “realistic” about the nature of the case and did not believe it would undermine the deeper political and trading relationship between Britain and China.

China, however, reacted toughly, saying the British should withdraw their criticism if they did not want to damage relations between the two.

In a statement that will resonate with ordinary Chinese, Beijing said “strong resentment” about illegal drugs in the country was based on “the bitter memory of history”, a reference to Britain's role in the 19th century in enforcing the import of opium into China.

“It is the common wish of people around the world to strike against the crime of drug trafficking,” the Chinese foreign ministry said.

The foreign ministry added that Beijing hoped “an individual criminal case” would not affect broader bilateral ties.

Mr Shaikh was executed on Tuesday in Urumqi, the capital of China's westernmost province of Xinjiang.

His family issued a statement saying it was “ludicrous” that their relative was required to prove his own mental disability, thought to be bipolar disorder.

China carried out more executions than the rest of the world put together last year, Amnesty International said.

Early signs of Chinese public opinion showed widespread approval of the execution, with most respondents on website Sohu.com, a popular portal, supporting it.

Even in the UK public opinion was at least somewhat divided, with readers of a popular British newspaper posting support online for a column suggesting the decision may have been justified.