A total of 821 criminal networks threaten to undermine the security of the European Union, according to the European police agency EUROPOL.
Professional gangs, many of which operate internationally, have more than 25,000 members, according to the report on organized crime presented to The Hague.
"Serious and organized crime is widespread and continues to pose a major threat to the internal security of the European Union," states Europol after studying data from 27 EU member states and 17 Europol partner countries.
The report focuses on the most dangerous networks and how they operate, describing them as "highly professional, flexible, controlling and destructive".
Europol named the powerful 'Ndrangheta family in Italy as a prime example, with profits from drug and arms trafficking being invested across Europe in properties, supermarkets and hotels.
The report emphasizes that Albanian criminal groups are mainly involved in the trafficking of heroin and cocaine.