The vast majority of pirate vessels illegally fishing off Sierra Leone are accredited to export their catches to Europe, an environmentalist group says.
An Environmental Justice Foundation report says West Africa has the world's highest levels of illegal fishing.
It says pirate fishermen fish inside exclusion zones, attack local fisherman and refuse to pay fines.
An EU spokesman said he was "very concerned" that illegally fished produce could enter Europe's markets.
The UK-based campaign group has called for vessels which break the law to be blacklisted.
It urges that weaknesses in EU regulations be addressed to stop illegal fish entering Europe.
"The EU is relying too heavily on the assurances of flag states that plainly are not monitoring their fishing fleets in West Africa," said EJF Executive Director Steve Trent.
"Authorities inspecting fish in European ports have very little reliable information on what is happening in the areas where it is caught.
"We must urgently improve communication between the EU and coastal States if we are serious about ending pirate fishing and protecting some of the world's most vulnerable coastal communities."
Oliver Drewes, spokesman for European Fisheries and Maritime Affairs Commissioner Maria Damanaki, told the Reuters news agency that if the abuses were confirmed, the offending vessels would be banned from exporting to the EU and barred from European ports.
