Politicians asked the British government on Thursday about rumours that a businessman whose murder sparked political upheaval in China may have been a spy and demanded to know why it took so long for ministers to be told of suspicions about his death.

Police in China initially attributed the death of Neil Heywood, 41, in a hotel room in the southwest Chinese city of Chongqing last November to cardiac arrest due to over-consumption of alcohol.

But this month authorities said they believed it was a murder and named the wife of Bo Xilai, a former Communist Party chief of China's south-western Chongqing city, as a suspect.

The British foreign ministry has since come under fire at home for being slow to demand that China investigate the case.

British media have also speculated Heywood may have been a British spy but Heywood's relatives and a British security source have denied there were any grounds for such rumours.

Richard Ottaway, chairman of parliament's influential Foreign Affairs Committee, wrote to Foreign Secretary William Hague demanding clarification.

I would be grateful if you would make clear what relationship the British Consulate-General Chongqing or the British Embassy in Beijing had with Mr Heywood before his death, wrote Ottaway, who is a member of Prime Minister David Cameron's Conservative Party.

Did he supply the British Consulate or Embassy with information, either on a formal or informal basis? he asked.

A security source said Heywood did not work for, or have a relationship with, Britain's intelligence services.

Hague released a detailed account this week of the British government's involvement in the Heywood case to counter accusations from politicians that it had not acted quickly enough to make its concerns public.

We see nothing improper or inconsistent in what he (Hague) said ... but we would like a bit more flesh on the bones, Ottaway told Reuters.

The Foreign Office had no immediate comment on Ottaway's letter but Hague had earlier rejected criticism over the speed of the government's response.

INQUIRY

Chinese officials notified British diplomats of Heywood's death on November 16, according to Hague's account. Foreign Office officials first heard on January 18 about rumours among British expatriates in China that there may have been suspicious circumstances surrounding his death.

However, Hague was not told about the case until February 7, the day after Wang Lijun, Bo's once-trusted police chief, fled to a U.S. consulate in an apparent attempt to secure asylum, alleging that Bo's wife was involved in Heywood's death.

Why were earlier rumours about Mr Heywood's death, which reached (Foreign Office) staff in January, not communicated to ministers immediately? Ottaway said, writing on behalf of a committee that includes politicians from all major parties.

The Foreign Affairs Committee has the power to open an inquiry and hold hearings into Heywood's death. Asked if it would do so, Ottaway said: Let's wait and see.

Heywood was poisoned after he threatened to expose a plan by Bo's wife to move money abroad, two sources with knowledge of a Chinese police investigation said this week.

On Tuesday, Hague said that ministers were not routinely told about the death of British nationals abroad but insisted that the government pressed repeatedly for an investigation.

We have asked for, we have demanded, an investigation. The Chinese authorities have agreed to conduct such an investigation, Hague said. We are pursuing this extremely carefully but vigorously.

(Additional reporting by William Maclean; Editing by Maria Golovnina)