Foreign Office asked China four times to investigate British businessman Neil Heywood's death

William Hague defends officials against charges they did not push for a Neil Heywood inquiry

The Prime Minister raised the matter yesterday with Li Changchun, a senior Chinese official visiting No 10 (Getty Images)

Foreign Office diplomats asked China to open a murder investigation into the mysterious death of a British businessman four times before the authorities eventually did so, the Foreign Secretary William Hague said yesterday.

Neil Heywood, who had close links to China's political elite, was found dead in a hotel on the outskirts of Chongqing on 15 November last year. His death was initially attributed to drinking too much alcohol but Chinese authorities have since alleged that he was poisoned on the orders of the wife of a major figure within the Communist Party.

Reports this week suggested that he was killed because he was allegedly going to reveal corrupt financial deals made by Gu Kailai, the wife of Bo Xilai, who was removed as the Chongqing party chief last month.

The scandal has plunged China's political leadership into a crisis and begun to test diplomatic relations between Beijing and London. The Foreign Office has been under pressure from MPs to explain whether it pressed hard enough for a full investigation into Mr Heywood's death.

In a statement yesterday, Mr Hague revealed that diplomats in China first began to hear rumours as early as mid-January that Mr Heywood had been murdered. In a bid to show that Britain began pressuring the Chinese straight away, Mr Hague said diplomats urged Beijing on four separate occasions to open a murder inquiry. The British embassy first asked officials from the Chinese foreign ministry on 15 February. Britain's ambassador followed up with a request six days later and the following week Chinese officials were asked again during a trip to London. Britain's ambassador made a fourth request on 22 March.

An investigation into Mr Heywood's death was eventually opened last month but only after compromising details became public knowledge. In February a high-ranking Chinese police officer sought asylum in the US consulate and said Bo Xilai's wife ordered Mr Heywood's poisoning. The allegations have led to the sacking of Mr Bo, who was tipped as a potential future party leader.

Yesterday, David Cameron raised the subject of the investigation into Mr Heywood's death with Li Changchun, a senior Chinese official who was visiting Downing Street.