A BRITISH businessman was poisoned after he threatened to expose a plan by a Chinese leader's wife to move money abroad, two sources with knowledge of the police investigation have claimed.

It was the first time a motive has been revealed for Neil Heywood's murder last November, a death that ended Chinese politician Bo Xilai's hopes of emerging as a top central leader and threw off balance the Communist Party's looming leadership succession.

Mr Bo's wife Gu Kailai asked Mr Heywood to move a large sum of money abroad, and she became outraged when he demanded a larger cut than expected, the sources claimed.

She accused him of being greedy and hatched a plan to kill him after he said he could expose her dealings, one of the sources said. Both sources say they have spoken to investigators in Chongqing, the south-western Chinese city where Mr Heywood was killed and where Mr Bo had cast himself as a crime-fighting Communist Party leader.

Prime Minister David Cameron is likely to discuss the murder with visiting Chinese official Li Changchun today. "It's likely to come up," his spokeswoman said.

Gu is in police custody on suspicion of committing or arranging Mr Heywood's murder, though no details of the motive or the crime itself have been publicly released, other than a general comment from state media that he was killed after a financial dispute.

They said Heywood was killed after he threatened to expose what she was doing.

The sources, who have have close ties to Chinese police, said officers suspect the 41-year-old was poisoned by a drink. They said Gu and Mr Heywood, who had lived in China since the early 1990s, shared a close relationship but were not romantically involved.