Recently retired Chinese NBA star Yao Ming is taking the fight against eating shark fins back to his homeland, where demand for the traditional delicacy is soaring despite efforts to ban their use and trade.

Yao and British tycoon Richard Branson made an appeal Thursday in Shanghai against eating shark fins, which are a staple of high-class Chinese banquets, to a group of 30 of China's richest and most influential businesspeople.

"When demand happens, the buying happens and the killing happens," said Yao. He says he is using his post-retirement free time to campaign against the slaughter of 1.5 million sharks a week that is taking some of the species close to extinction.

The event, sponsored by the conservation group WildAid, is aimed at starting a conservation movement in China "not just to protect the sharks but to protect tigers, and to protect other species that are in peril of extinction," Branson said.

Critics say fishermen kill more than 70 million sharks each year for their fins, which can sell for $700 a pound (450 grams), while the soup can cost $80 a bowl. Usually, the fins are cut from the sharks and their bodies discarded, leaving them to die.

Although there have been moves to ban the trade and consumption of shark fins in California and elsewhere, 95 per cent are consumed in China.

"There's been a massive increase in shark fin soup and the killing of sharks," said Branson, whose Virgin Airlines bans transport of shark fins. "The world is getting wealthier, particularly in China people are getting wealthier, and they can now afford to buy shark fin soup."

"We're trying to get other businesses to ban the transportation of shark fins," he said.

While shark fins have been used to make soup for hundreds of years, until recently consumption was limited to a small elite, said Yao, who gave up eating shark fin in 2006 and says he avoids events where it is served.

About 20 countries and regions have imposed regulations on finning or commercial shark fishing. Earlier this month, California imposed a ban on the trade. China regulates dealings in and harvesting of sharks but has not banned it.

"As far as shark finning is concerned the best way is to ... ban altogether shark fin soup from states and then countries. That's perhaps the only way to save the shark in the long term," Branson said.

Elaine Kurtenbach reports for the Canadian Press.