The sale of organs taken from executed prisoners appears to be thriving in China, an undercover investigation by the BBC has found.

Organs from death row inmates are sold to foreigners who need transplants.

One hospital said it could provide a liver at a cost of £50,000 ($94,400), with the chief surgeon confirming an executed prisoner could be the donor.

China's health ministry did not deny the practice, but said it was reviewing the system and regulations.

'Present to society'

The BBC's Rupert Wingfield-Hayes visited No 1 Central Hospital in Tianjin, ostensibly seeking a liver for his sick father.

Officials there told him that a matching liver could be available in three weeks.

One official said that the prisoners volunteered to give their organs as a "present to society".

He said there was currently an organ surplus because of an increase in executions ahead of the 1 October National Day.

China executes more prisoners than any other country in the world. In 2005, at least 1,770 people were executed, although true figures were believed to be much higher, a report by human rights group Amnesty International said.

In March, China's foreign ministry admitted that organs from prisoners were used, but said that it was only in "a very few cases".

Spokesman Qin Gang said that the organs were not taken forcibly, but only with the express permission of the convict.

But whether prisoners really are free to make up their own minds on organ donation just before they are executed is not at all clear, our correspondent says.

In April 2006, top British transplant surgeons condemned the practice as unacceptable and a breach of human rights.

But the No 1 Central Hospital carried out 600 liver transplants last year, our correspondent says, and the organ transplant industry has become big business.