at the Chinese Communist Party's 18th congress later this year.

The audio recording, which was posted on the internet, seems to have involved senior officials in the western city of Chongqing.

They heard how the city's police chief, Wang Lijun, told Mr Bo in January that his family was being investigated. The politician apparently reacted angrily and demoted Mr Wang, disregarding established practices.

There have been rumours about Bo Xilai's family for some time, many centred on his son, Bo Guagua.

He studied at one of Britain's most expensive private schools, Harrow, before going on to Oxford University.

Photographs that appear to show him enjoying himself at parties have whizzed around internet sites.

Speaking at a political meeting just before he was removed from office, Bo Xilai hit back at the rumours surrounding hisfamily.

He claimed that his wife and son had no assets, adding that his son's schooling was paid for by a scholarship.

Reports that Bo Guagua drives a red Ferrari were also false, he said.

US consulate visit

But the audio recording of the Chongqing meeting suggests the rumours were at least significant enough for an investigation.

Those at the gathering were told that after his demotion, Mr Wang fled to the US consulate in Chengdu, a few hours' drive from Chongqing, because he feared for his own safety.

The police chief's visit to the consulate is already an established fact. This recording suggests the reason behind it.

Mr Wang eventually came out of the consulate and was detained.

It is difficult to verify the authenticity of the recording - or how it was made and