Campaigners want China to continue cracking down on tiger poaching
Illegal "tiger bone wine" is still being made and sold by some animal parks in China, say campaigners.
The Environmental Investigation Agency says staff at two parks offered to sell the drink, made from carcasses soaked in rice wine, to its researchers.
The trade in parts of the endangered species has been subject to an international ban since 1987, and has been outlawed in China since 1989.
Despite global conservation efforts, tiger numbers continue to decline.
There are an estimated 3,500-7,500 tigers left in the wild, compared with roughly 100,000 at the start of the 20th Century.
'Closed market' sales
The UK-based NGO said its investigators found that the wine, deemed to be a health tonic to treat conditions such as arthritis and rheumatism, was being openly advertised at the parks.
Staff said the wine was made from tigers that had died after fighting with other big cats at the venues.
One park produced what they said was a government permit that allowed the sale of the tiger-derived wine on the premises, but the EIA researchers said it was not possible to verify whether the permit was genuine.
The EIA said a senior worker, when questioned by its researchers, said that she was aware that the tigers were a protected species and trading of any part of the animals "in the open market" was prohibited.
But the agency said that she went on to explain that the permit allowed "closed market" sales of the wine; in other words, it could be sold from the park's premises.
Debbie Banks, head of the EIA's tiger campaign, called on the Chinese authorities to close down the illegal trade.
"We want other parks with similar tiger attractions to be investigated to see how widespread this tiger-bone wine-making practice is," she said.
"We also want the authorities to give a clear message to the business community that this illegal trade will not be tolerated."
Conservationists estimate that tigers now only occupy just 7% of their historical range, primarily as a result of habitat loss, hunting and poaching.
They believe that there are just 2,500 breeding adults left in the wild and without more resources made available to protect the animals, the cats face an uncertain future.
Since the 1980s, a number of "tiger farms" have been set up in China. These establishments are believed to house about 5,000 captive tigers, possibly more than remain in the wild.
During last year's high-level summit of the global Convention on the International Trade in Endangered Species (Cites), the Chinese delegation raised the possibility of ending its domestic ban in order to allow the use of farmed tiger parts.
They argued that this would prove to be the most sustainable option because it would satisfy the demand from traditional medicine practitioners without threatening the wild tiger population.
Although this approach was supported by some conservation groups, others warned that it would undermine efforts by the Chinese government to curb poaching.
They said that it would be cheaper to kill a wild tiger than to rear a captive one, and it would be very difficult to tell the difference between the two.
"Lifting the ban would increase demand and lead to a surge in poaching," said Ms Banks.
"It would be far too easy to launder their skins, bones and parts among those from legalised tiger farms. This would effectively declare an open season on wild tigers."