FILE PHOTO: Ana-Maria Ciulcu, a Romanian, holds European Union pet passports in Bucharest April 12, 2014. Picture taken April 12, 2014. REUTERS/Bogdan Cristel/File Photo

BRUSSELS (Reuters) - European Union lawmakers backed measures on Tuesday to clamp down on abuse of EU pet passports by criminals and gangs that illegally trade cats and dogs.

The environment committee of the European Parliament voted unanimously for a resolution calling for stricter measures to combat illegal trafficking of pets.

Lawmakers are concerned that criminal gangs are exploiting the pet passport system and that animals are transported in unacceptable conditions, many without vaccinations against diseases such as rabies. Studies show many illegally trafficked pets come from eastern Europe.

The pet passport - a document that shows animals are vaccinated against rabies — is designed to help people travel with their pets and not for trade in animals.

The resolution calls for an EU-wide mandatory system of registration for cats and dogs, and for authorized animal breeders and sellers.

Lawmakers want tougher law enforcement and penalties for illegal traders, the veterinarians that support them and the people or public bodies that supply counterfeit pet passports.

They also want more to be done to inform potential buyers of the risks and encourage people to adopt rather than buy pets.

Illegal breeders, the resolution says, often set lower prices than registered breeders. The breeders suffer as a result, as do member states with reduce tax income.

The full parliament is expected to vote on the resolution in February and pass its recommendations to the European Commission, the executive body that drafts laws.