Dog breeders who sell puppies under eight weeks old will face jail in a new crackdown on "backstreet breeders".
People who breed and sell more than two litters of puppies a year will require a formal licence and a "strict welfare criteria" will apply to small breeders, including those who sell pets on the internet, as well as commercial breeders.
Anyone who breaks the rules faces an unlimited fine and up to six months in prison.
Announcing the new tougher measures, Environment Secretary Andrea Leadsom said: "For thousands of puppies born each year to irresponsible breeders, from smaller operations to larger puppy farms, their first weeks are spent in cramped and squalid conditions without the care and attention they need.
The move follows the case of a puppy farm gang who were handed a suspended sentence for selling sick dogs they had kept in cages and dark sheds.
They had admitted advertising the animals as home-bred, well cared for puppies and were convicted of fraud.
Animal welfare charities welcomed the news as a "step in the right direction".
Dogs Trust veterinary director Paula Boyden said: "We are particularly pleased that it will be illegal to sell a puppy below the age of eight weeks and that there will be tighter licensing rules which will require sellers of pets to display their licence when advertising."
Kennel Club secretary Caroline Kisko added: "We have called for a ban on third party sales, and refuse to register puppies being sold to third parties, but this new rule is a step in the right direction.
"We also welcome the requirement for pet sellers to provide written information about the animals they sell and for those who sell pets online to display their licence number."
Battersea Dogs & Cats Home also praised the plans as a "welcome first step".
The charity's chief executive Claire Horton said: "It's high time we put a stop to the many undercover backstreet breeders and large-scale puppy farmers that profit from their cruel treatment of these animals."
Neil Parish MP, chairman of the Environment, Food and Rural Affairs Committee, said not banning the third party sale of dogs in the new legislation is a "lost opportunity".
"The Government's own advice for a buyer to see a puppy with its mother is contradicted by the ability of third parties to sell puppies," he said.
"While I welcome a new licensing regime for breeders, the committee will be disappointed that the Government has decided to apply it to anyone breeding three litters or more."
RSPCA's tips before getting a puppy:
- Research the breed that you want
- Research the breeder
- Speak to your vet
- Visit the RSPCA website for a puppy contract
- Consider having a rescue dog