A charity has uncovered a "high level of corruption" and "shocking" animal welfare following its investigation into the trade of puppies from eastern Europe to the UK.

The Dogs Trust has released footage that it says shows criminal breeders, vets and transporters in Hungary and Lithuania abusing the Pet Travel Scheme, which allows pet dogs, cats and ferrets to enter Britain without quarantine.

European vets were caught on camera creating false pet passports and rabies vaccination records.

The charity revealed ­under-age puppies slipped through the net undeclared due to a lack of checks at ferry ports and borders, enabling breeders to make up to £100,000 a year.

It also found some puppies were forced to make journeys of more than 1,000 miles in appalling conditions without suitable treatments or vaccinations, increasing the risk of spreading diseases such as rabies in the UK.

Paula Boyden, Dogs Trust veterinary director, said: "Unsuspecting British shoppers will continue to buy puppies online that may have been brought into the country illegally, meaning the risk of unknowingly bringing a puppy from eastern Europe with diseases and behavioural problems into the home is very real.

"Dogs Trust is urging anyone considering buying a puppy to stop and think, 'Where is my dog coming from?'"