The RSPCA on Friday warned dog-lovers to be aware of the dangers of "puppy trafficking", saying people were taking a risk if they bought their puppies from the internet, newspapers ads or even some pet shops.

The animal welfare charity said trafficked puppies risked having illnesses or behavioural problems making them unsuitable pets, and said owners needed to know where their dog came from.

In a test it conducted, out of six puppies it purchased, two were found to have potentially fatal illnesses. One, a King Charles spaniel, died after two weeks.

The RSPCA said 73 percent of vets were now concerned about the trade in puppies while it had received more than 700 calls in 2007 about puppies that had become ill after being purchased or were not as described in adverts.

Mark Evans, RSPCA Chief Veterinary Adviser, said some dogs were used as "breeding machines", producing litter after litter which were then passed on to unscrupulous traders or sold to unsuspecting customers.

"The RSPCA believes that many are likely to have been exposed to disease and may become seriously ill, or even die, within days or weeks of entering their new home," he said.

About 1,000 puppies are imported from Ireland to Wales every week before being sold on, the RSPCA said. However, just 2 percent of owners believed their pet was from Ireland.

Evans said prospective owners needed to do their homework before buying a puppy, and advised them to go to rescue centres or respected breeders.

"Puppy trafficking is a despicable, profit-driven business," Evans said. "We want the dog-loving public to destroy the puppy trafficker's market."