The Environmental Investigation Agency said at an endangered species conference in Bangkok more than 10,000 ads for ivory were running on Google's Japanese shopping site. The organization said it has contacted the search giant asking for the ads to be removed.
The EIA, based in London, said the majority of the ads were for "hanko" -- name seals Japanese people use to sign official documents, which are often inlaid with ivory lettering.
The ads go against Google's own policies against the promotion of elephant or whale products, the EIA said.
"We were really shocked to be honest, to find that one of the world's richest and successful technology companies with such incredible resources had taken no action to enforce their own policies," EIA's Allan Thornton told BBC News, "especially given that elephants are being slaughtered across Africa to provide these trinkets for the public in Japan."
Google has acknowledged the ads violated its own terms, the EIA said.
In a statement, 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."
The EIA said it informed Google Feb. 22 of the problem but the ads are still up and running.
Google has not responded yet, the EIA said.