It also said unregulated domestic markets in countries such as host nation Thailand were a significant factor in the trade, which conservationists say is soaked in the blood of slaughtered elephants.
The report to the Convention on International Trade in Endangered Species (CITES) weakened Kenyan assertions that legal trade in ivory would tempt poachers to launder their "dirty" ivory with legal supplies.
"The ivory market in China continues to be the most important influence," said the report, prepared by the Elephant Trade Information System (ETIS).
It was presented ahead of a Namibian bid to get permission for annual ivory quotas of 2,000 kg from CITES, which regulates global trade in wild flora and fauna.
The ETIS report looked at records from 75 countries or territories of 9,426 seizures of illicit elephant products from 1989 - when CITES first imposed a global ban on trade in ivory - and 2004.
It estimated that 226 tons of ivory were seized globally during that period.
"The data show that the volume of ivory seized declined from 1989 to 1994, then gradually increased from 1995 onwards, though never to levels prior to 1992," it said.
"If Chinese demand is removed, the trend line is essentially flat from 1994 onwards, indicating that this single market alone accounts for the increase in illegal trade in ivory in recent years," it said.
It noted that CITES allowed three African countries to sell ivory to Japan in 1999. In 2002, conditional permission for one-off sales were granted to South Africa, Namibia and Botswana, but those sales have not occurred yet.
But the report said there was no clear link between these events and a surge in ivory seizures - a key contention of Kenya, which is staunchly opposed to any renewed trade on the grounds that it will put its elephants and even its rangers at risk from ruthless and heavily armed criminals.
"The ivory seizure data in ETIS continues to demonstrate a strong correlation between illegal trade in ivory, domestic ivory markets and poor regulation," it said.
"Cameroon, China, the Democratic Republic of the Congo, Ethiopia, Nigeria and Thailand are most highly implicated in the illicit trade in ivory," it said.
But it lauded China for making "commendable" efforts to tackle the problem.
African countries pledged a continent-wide crack down on their flourishing ivory markets.
A Kenyan attempt to place a moratorium on ivory sales was defeated ahead of the Namibian vote.
Kenya says the initial ban on ivory stemmed an elephant massacre which saw its population of the massive beasts fall to 16,000 in 1989 from about 168,000 in the mid-1970s. (Reuters)
