A conservation group claims that Google has something in common with illicit ivory traders in China and Thailand - it says the internet search giant is helping fuel a dramatic surge in ivory demand in Asia which is killing African elephants at record levels.
The Environmental Investigation Agency, a conservation advocacy group, said in a statement that there are some 10,000 adverts on Google Japan's shopping site which promote the sale of ivory.
About 80% of the ads are for "hanko" - small wooden stamps 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 typically inlaid with ivory lettering.
The EIA said Japan's hanko sales are a "major demand driver for elephant ivory (and) have contributed to the wide-scale resumption of elephant poaching across Africa".
Google said in an emailed response to the Associated Press: "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."
The EIA said it had written a letter to Google chief executive Larry Page on February 22 urging the company to remove the ads because they violate Google's own policies. It said Google had not responded to the letter or taken down the advertisements.
"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 Allan Thorton, the US-based president of the EIA.
Google's advertising policies state that Google "doesn't allow the promotion of products obtained from endangered or threatened species", including elephant tusks, rhino horns and products made from whales, sharks and dolphins. Mr Thorton said the policies were laudable "but sadly these are not being enforced and that's devastating".
Concerned internet shoppers have alleged that ivory is being sold on other sites as well, including eBay. Some objects now offered for more than 1,000 US dollars (£665) apiece are marketed as "ox bone" or "faux ivory".