Thousands of pet owners are buying dogs bred under cruel conditions in puppy farms, without even knowing it.
The charity The Dog's Trust said up to 900,000 people have bought a dog from a puppy farm.
Farmed dogs are often not given enough room to move about and are taken away from their mums too early. This means they can suffer health problems or be unhappy.
The charity said pet owners should check where a puppy has come from.
The Dog's Trust said farmed puppies are kept in cramped conditions a bit like battery hens
It said puppies sold in pet shops and garden centres, or advertised in newspapers and on the internet are often farmed.
Instead the safest option is to buy a dog from a good breeder and ask to see the puppy's parents and kennels where it lives.