The Dogs Trust, which has rescue centres across the South East, says demand for puppies during lockdown has led to a huge rise to the cost of some of the UKs most desirable dogs.
The asking price for breeds like Pugs, English bulldogs and Chow Chows shot up between March and June.
The charity says these breeds are the most likely to be illegally imported in to the country through places like Dover.
Claire Calder from Dogs Trust says: "During the lockdown period we saw a shift to commercial imports of these puppies. So it is essentially business as usual for illegal importers. We know it is happening and we're just really worried because the welfare of the puppies often isn't considered, and when there is such a profit to be made."
The charity has reviewed advertisements from the last three years on some of the UK's largest classified advertising websites, and prices for Pugs, Dachshunds and Chow Chows have never been higher, whilst English and French Bulldogs have also seen significant price hikes.
The most expensive of the breeds, English Bulldogs, advertised for as much as £2,140 on average in June compared to an average of £1,637 in March - although some listings reached as high as £9,000.
Dogs Trust is urging people to be alert to the perils of buying via online adverts, to avoid being duped, or Dogfished, and to remind potential new owners to never hand over a deposit before seeing the dog in person**. This comes against the backdrop of people contacting Dogs Trust to say they have been victims of scams during coronavirus lockdown.