A British businessman found dead in China was killed with cyanide, it has been reported.
Neil Heywood was murdered on the orders of a fallen Communist Party chief, according to the Mail on Sunday.
The newspaper quoted "respected Mandarin-language websites" saying Mr Heywood, 41, died from cyanide poisoning after allegedly having an affair with lawyer Gu Kailai, wife of Bo Xilai, seen until recently as a future leader of China.
Mr Heywood was found dead on November 15 in Chongqing, in central China.
Britain asked China to investigate his death and it emerged last week that Mrs Gu was being probed for "intentional homicide".
The Mail on Sunday said it was alleged that Mr Heywood was murdered after helping Mrs Gu to siphon nearly £800 million of assets overseas.
A city official has allegedly confessed that he prepared the poison and handed it to an employee of Mr Bo, who administered it to Mr Heywood on the party chief's instructions.
Mr Heywood was a friend of the family of Mr Bo, a former rising star in Chinese politics who served as local party chief in Chongqing.
At the time, Chinese officials said the British expat died of "excessive alcohol consumption".
But friends questioned this, saying the businessman was not a heavy drinker.
In February, Mr Bo's former police chief Wang Lijun sought refuge in the US consulate in China.
It is thought he made a number of claims against the politician and Mrs Gu, including her alleged role in Mr Heywood's death.
State media reported on Tuesday that Mrs Gu and Zhang Xiaojun, an orderly at Mr Bo's home, had been arrested.
Meanwhile Mr Bo has been suspended from the Communist Party's 25-member Politburo amid allegations of "serious discipline violations".
A Foreign Office (FCO) spokeswoman said yesterday: "We are aware of the latest media reports. As there is an ongoing
Chinese police investigation into this case it wouldn't be appropriate to comment further. We remain in close touch with the Chinese authorities and Mr Heywood's family."
Saturday's edition of The Times said the Foreign Office was facing increasing questions over delays in its intervention.
It said it had emerged that a British diplomat and two Chinese policemen attended Mr Heywood's cremation in Chongqing shortly after he was killed.
But the British did not raise questions with the Chinese until three months later, despite locally based British businessmen urging the Foreign Office to intervene, the newspaper said.
An FCO spokesman said: "As we became more concerned about this case, including following suggestions from the business community, we took the decision to ask the Chinese authorities to launch an investigation.
"We acted as soon as we thought concerns about the case justified it.
"We are pleased that the Chinese have now launched that investigation. We were in constant contact with the family throughout and kept them informed of our actions."
He said: "We did ask the Chinese to hold an investigation and we are pleased that they are now doing that.
"It is very important we get to the truth of what happened in this very disturbing case, this very tragic case."
Mr Heywood had lived in China for 10 years and was fluent in Mandarin. He had two children with his Chinese wife.
Saturday's Daily Mail said that his wife, Wang Lulu, had visited the British embassy in Beijing on Friday, and was understood to have asked for a visa to go to the UK with her children.
n March ITV said that Heywood worked for a corporate intelligence firm which was set up by former MI6 officers, and quoted sources who speculated that he may have been a spy.
Last week ITV reported that Heywood may have "fallen out" with Bo's wife, a lawyer named Gu Kailai, before he died.
An FCO spokesman said: "We do not discuss the visa status of individuals."