Nearly 20 per cent of the samples were found to have come from elephants killed after 1989, when a global ivory trade ban went into effect.
When Oxford University's carbon testing unit examined the items, they found that 75 percent of them were fake antiques being sold illegally.
All the pieces bought in Bulgaria, Italy and Spain were illegal, as were large majorities of the items in France, the Netherlands and Portugal.
The items were purchased from both antique dealers and private sellers in 10 countries across Europe.
Campaigning group Avaaz, which sponsored the research, purchased over 100 ivory items in 10 European countries to determine their real age.
Illegal ivory has been found on sale in 10 European countries, contravening worldwide efforts to cut down on the trade.
Avaaz said that the study's results, which include items sold in shops and online, shows that the European Commission should do more to control the illegal ivory market.
Bert Wander from Avaaz said: "It's sick". And 45% of the ivory samples came from tusks that grew in the 1970s and 1980s, which makes it probable that the elephants were killed after the 1989 CITES ivory ban.
The finding was not as surprising to Avaaz campaigners, however.
Avaaz said the findings, which echo other research that has found illegal ivory objects on sale in the United Kingdom and elsewhere, showed that Europe should do more to investigate and control the ivory trade. It must spark the end of this bloody trade. "Every day the sale of these trinkets continues is a day closer to wiping out majestic elephants forever".
How many ivory markets are left?
An exhibition at the European Parliament on Tuesday calling for a ban on ivory trade in Europe.
Avaaz urged in a statement that "the Commission should close the antique ivory loophole, end ivory exports from Europe and shut down the EU's internal trade in raw tusks".
The EU legal market in ivory may consist mainly of small items, but they add up to several tonnes sold each year.
Three-quarters of the items were dated to after 1947. "For the first time, this study shows that this legal trade is covering up an illegal trade", the campaigners said, calling on the European Union to take action.
Last month, the European Parliament called for a complete ban on the ivory trade. And according to Avaaz, the study "provides a clear and categorical answer to that question: they do not".
"The Illegal Wildlife Trade Conference in London in October could be the flawless moment to show the leadership we are asking for". EURACTIV's partner Journal de l'Environnement reports. Savannah elephants have likewise been hard hit in some strongholds, with losses of 60% in Tanzania alone in the past five years.
China has also banned all trade except what it terms "genuine antiques".