Foreign Secretary William Hague has come under pressure from MPs to explain why Britain did not intervene sooner over the murder of businessman Neil Heywood in China.
The Foreign Affairs Select Committee wrote to Mr Hague asking why ministers were not immediately informed about rumours that surfaced in January that there were suspicious circumstances surrounding Mr Heywood's death.
In a letter from committee chairman Richard Ottaway, it also raised speculation about Mr Heywood's "profession", and whether he had supplied information to the British Consulate or Embassy. State media reports in China have suggested that investigations by authorities there indicate Mr Heywood, 41, was a victim of homicide.
He was a friend of the family of Bo Xilai, a former rising star in Chinese politics who served as local party chief in Chongqing but was suspended from the Politburo in April amid allegations of "serious discipline violations".
Mr Heywood died in the city of Chongqing last November, and Chinese authorities initially said it was down to alcohol overconsumption. Mr Hague said this week that Foreign Office staff were aware on January 18 of rumours that there may have been suspicious circumstances.
But it was not until after a former Chongqing vice-mayor and chief of police Wang Lijun raised the concerns with the US consulate on February 6 that officials informed Mr Hague. The UK subsequently asked China to investigate, which it has now promised to do.
Unconfirmed media reports suggest that police suspect Mr Heywood may have been poisoned after threatening to expose a plan by Bo's wife Gu Kailai to move money abroad.
In his letter, Mr Ottaway wrote: "From your statement, it appears that ministers were informed of Neil Heywood's case only after allegations were made by Wang Lijun on February 6. Why were earlier rumours about Mr Heywood's death, which reached FCO staff in January, not communicated to ministers immediately?"
The Tory MP also asked the Foreign Secretary to clarify Mr Heywood's relationship with the British Consulate-General in Chongqing and the British Embassy in Beijing.
"For instance, did he supply the British Consulate or Embassy with information, either on a formal or informal basis?"