The wife of Bo Xilai, the former political leader whose downfall sent shockwaves through China, has been charged with murdering a British businessman, state news agency Xinhua said Thursday.

Gu Kailai, a former international lawyer whose husband was one of China's most promising political leaders until his dramatic fall from grace this year, will face trial for intentional homicide, Xinhua reported in a brief dispatch.

Zhang Xiaojun, previously described as an orderly who worked for the high-flying couple, will also be prosecuted on the same charge, it said, citing authorities.

Xinhua said there was "irrefutable and substantial" evidence that the pair had poisoned Neil Heywood, a British businessman who had commercial dealings with Bo and his wife.

"Investigation results show that Bogu Kailai, one of the defendants, and her son surnamed Bo had conflicts with the British citizen Neil Heywood over economic interests," said Xinhua, using Gu's married name.

"Worrying about Neil Heywood's threat to her son's personal security, Bogu Kailai along with Zhang Xiaojun, the other defendant, poisoned Neil Heywood to death."

Little is known about the nature of Heywood's relationship with the couple's son Bo Guagua, although he is reported to have helped secure a place for him at Harrow, the exclusive British school that Heywood himself attended.

The younger Bo recently graduated from Harvard.

Heywood's death in a Chinese hotel room last November was initially blamed on excessive alcohol consumption.

Gu and Zhang have been interrogated and will be tried at a court in the eastern Chinese city of Hefei "on a day to be decided", Xinhua said, adding that their families had been informed.

If convicted, Gu faces the death penalty, although this is often commuted in the case of high-profile defendants.

The scandal, which first came to light in February, has sent shockwaves through the highest echelons of power in China and led to Bo being sacked from his post as Communist Party leader of the megacity of Chongqing.

Analysts say it has exposed deep divisions within the Communist Party ahead of a crucial, once-in-a-decade leadership transition due to take place at a party congress this autumn.

Li Datong, a former editor at the state-run China Youth Daily who was removed for reporting on sensitive issues, said China's leaders would be keen to settle the case before then.

"The whole thing should be handled before the 18th Party Congress. Everything has to be resolved -- Bo Xilai, Gu Kailai, everything," he said.

"They cannot leave this problem for the next leadership. It has to be handled now."

Li said the case had only come out into the open as it did because Wang Lijun, a senior official in Chongqing, had gone to a US consulate in southern China to express his suspicions about Bo and his family.

"No one would have known of this case without Wang Lijun. The people would not know, the party would not know. This is why it exploded," he said.

"This time (the Party) was unable to cover it up. It was too big for them to cover up."

Bo, the son of a revered Communist revolutionary, had earned a national profile with a draconian crackdown on criminal elements in Chongqing and a "red revival" campaign marked by the mass singing of old Maoist-era songs.

Many analysts saw the moves as a bid for entry to China's inner circle.

But the rapid unravelling of his fortunes has exposed a harsh factional reaction against the charismatic and ambitious leader, and the affair has been seen as a huge embarrassment for the party.

He is thought to be under house arrest and is being investigated for corruption. He has been stripped of his senior positions with the ruling Communist Party, although he remains a member.

Thursday's announcement came a little over a week after Patrick Devillers, a French architect said to have been close to Gu, travelled to China to assist in the official inquiry.

Devillers, 52, is understood to have been a business associate and friend of Bo and his wife, although his exact role is unclear.

He is believed to have first crossed paths with the couple in the 1990s, when Bo hired him to do some architectural work in the Chinese city of Dalian.

He was detained in Phnom Penh, where he had been living, on June 13 at Beijing's request and boarded a flight to China after he was released by Cambodian authorities.

Cambodian officials and the French foreign ministry have stressed it was Devillers' own choice to help Beijing with its investigation. China has so far made no comment.