Google Ivory Adverts 'Against Own Policies'
Google has been accused of helping to increase the demand for ivory by running adverts promoting the sale of the product.
The Environmental Investigation Agency (EIA) said illicit ivory traders in China and Thailand were benefiting from the killing of African elephants at record levels.
Google was a party to the trade because there were around 10,000 ads on Google Japan's shopping site that promote the sale of ivory, the conservation group said.
About 80% of the ads are for "hanko", small wooden stamps that are widely used in Japan to affix signature seals to official documents. The rest are carvings and other small objects.
Hanko are used for everything from renting a house to opening a bank account. The stamps are legal, and are typically inlaid with ivory lettering.
The EIA said Japan's hanko sales were a "major demand driver" for elephant ivory and had contributed to the widescale resumption of elephant poaching across Africa.
It said it had written a letter in February to Google CEO Larry Page urging the company to remove the ads because they violate Google's own policies but Google had neither answered nor taken down the adverts.
"While elephants are being mass slaughtered across Africa to produce ivory trinkets, it is shocking to discover that Google, with the massive resources it has at its disposal, is failing to enforce its own policies designed to help protect endangered elephants," said EIA president Allan Thorton.
In an email to the AP news agency, Google said: "Ads for products obtained from endangered or threatened species are not allowed on Google. As soon as we detect ads that violate our advertising policies, we remove them."
Curbing the trade in so-called "blood ivory" is at the top of the agenda of the 178-nation Convention on International Trade in Endangered Species, or Cites, which is meeting in Bangkok this week to discuss how to protect the planet's biodiversity by regulating the legal trade of flora and fauna and clamping down on smuggling.
In a video message played at the opening of the summit, the Duke of Cambridge urged delegates to do more to tackle the illegal killing of the African elephant and rhino.
"We must do more to combat this serious crime if we are to reverse the current alarming trends. If not, we could soon see some populations of these creatures, or even an entire species, disappear from the wild," he said.
"We simply must not let this catastrophe unfold. Our children should have the same opportunity that we have to experience wildlife in its many beautiful and varied forms."
Around 70 years ago, up to five million elephants are believed to have roamed sub-Saharan Africa. Now, just several hundred thousand are left.
Over the past few years, as Asian economies have grown and demand for ivory has risen, the slaughter of elephants has reached its worst level in more than two decades.
Last year alone, some 32,000 elephants were killed in Africa, according to the Born Free Foundation, which says black-market ivory sells for around $1,300 (£858) per pound. Much of it ends up as tourist trinkets and carvings.
Cites banned the international ivory trade in 1989, but the move did not address domestic markets.