He said the resurgence in demand was being led by the rapidly opening mainland market.

Green groups also warned Hong Kong cannot ignore its historic links with the illegal ivory trade, which reached significant levels at the end of the 19th century.

Local investigators say the ivory seized two weeks ago was old and had possibly been stockpiled for years before being repackaged as mainland demand increased.

CITES - of which China is a signatory - is an international agreement between governments. Its aim is to ensure international trade in specimens of wild animals and plants does not threaten their survival.

'At the time of the ivory trade ban under CITES, many economists predicted the impact of the ban would be immediate and trade volumes would decline; but if demand remained, then over time things would pick up again,' Mr Milliken said.

'In fact, it appears to be the case, and that demand in China has increased due to the economic growth there.

'Our reports identify China as the most important influence on this trend, although we want to acknowledge the Chinese government recognises this problem and is putting considerable effort into interdicting illicit shipments of ivory into China. Hong Kong emerges as of secondary interest in our reports, but certainly a place to keep an eye on given its historical association with the ivory trade.'

Customs seized 81 elephant tusks from a fishing boat in local waters. The tusks were found when Customs patrol boats carried out a spot check on a Hong Kong-registered boat on its way to Zhuhai.

The ivory was stashed in an empty fuel tank in the 20-metre vessel, said Gary Kwok, the divisional commander for the Customs Marine Enforcement Division.

Two men were arrested on the vessel - the master from Hong Kong and a crewman from the mainland - after the seizure. They were later charged. It is believed the tusks are from African elephants and were being smuggled into the mainland, where they would have been sold as unworked ivory or worked into chopsticks, jewellery or carvings.

The ivory was worth about $2,000 a kilogram unworked, and up to 10 times as much after being crafted, Mr Kwok said.

The haul also supported recent warnings by another international wildlife monitoring group, the Environment Investigation Agency (EIA), of heavy poaching of elephants in Africa and that Far East ivory markets are stirring.

The EIA said there was evidence that antique markets provided outlets for carving factories to sell smuggled ivory.

It said that in Guangdong, large quantities of ivory were sold openly in various outlets, hotels and government-owned friendship stores.

Government endangered species protection officer Boris Kwan Sai-ping said that despite the recent seizure, they had no evidence ivory smuggling was on the rise.

Mr Kwok said the SAR had tough regulations governing ivory trade and up until April, there were 256 tonnes of ivory stored in Hong Kong. The law requires ivory traders to register their stock following the 1990 ban.

A spokesman for the Hong Kong and Kowloon Ivory Manufacture Association said the local ivory industry had been dead for many years. But he admitted there had been an increase in the number of ivory shops opening in Guangzhou.

An ivory trader said smuggling had increased because of demand on the mainland. He said most of the tusks were from African elephants and Hong Kong was a re-export centre for the mainland.