"It is a vast, a varied trade ranging from smuggling of rare medicinal plants to butterflies to peafowls to tigers and it is difficult to predict how big it is, but the threats and dimensions suggest that the trade is increasing."

The tiger is facing the threat of extinction with early results from a new census suggesting there could be as few as 1,500 tigers left in India, compared to a century ago when there were around 40,000.

Leopards, rhinos, reptiles, birds and insects as well as rare species of trees and plants are also being smuggled into southeast Asian countries and China.

Wildlife experts say tiger and leopard parts are in great demand in China and other Asian countries. They are wanted for their skins, which are worn during festivals, as well as for their bones and body parts which are used in traditional medicines.

Sinha said China's booming economy had led to more demand for such expensive products. Some experts estimate that a single tiger skin can cost $20,000 on the international market.

"I think it's fair to say that the demand for wildlife parts in China is one of the biggest threats to India's biodiversity," said Sinha.

One of the biggest seizures in India was made in 2000, said Sinha, when a truck was found to be carrying 18,000 leopard claws, 132 tiger claws, four tiger skins, 70 leopard skins, 221 blackbuck skins, 150 kg (330 lb) of leopard and tiger bones and a dried leopard penis.

But seizures were often accidental, said Sinha, and not driven by intelligence. Efforts to convict the culprits were often limited to the primary offender, he added.

"At the moment, our law enforcement role stops at the offender we catch with the goods. We need to look beyond that," said Sinha. "We need to step up our intelligence and we have to go after the big-wigs ... only then can we save our wildlife."

Those involved in the trade are mostly highly organised cross-border criminal syndicates and involve a large supply chain -- ranging from the forest dweller in India who kills the animal, to transporters, smugglers and ultimately the buyer.