A new law aimed at cracking down on so-called puppy farms in England is being presented to Parliament on Monday.
Known as Lucy's Law, it will ban the sale of kittens and puppies from third parties from spring 2020, making buyers deal with breeders directly.
Environment Secretary Michael Gove said the new rules would give animals "the best possible start in life".
The RSPCA said it was "absolutely thrilled" with the legislation - but stressed it required enforcement.
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The new law would require animals to be born and reared in a safe environment, with their mother, and to be sold from their place of birth.
The rules, which will apply to England, are also designed to deter smugglers who abuse the Pet Travel Scheme to bring young animals into the UK to be sold.
Named after Lucy, a Cavalier King Charles Spaniel who died in 2016 after being poorly treated on a puppy farm, the ban is scheduled to come into force on 6 April next year, the Department for Environment, Food and Rural Affairs said.
Marc Abraham, Lucy's Law campaigner and founder of Pup Aid, said: "I'm absolutely thrilled that Lucy's Law is now being laid in Parliament and will come into effect from April 2020.
"Lucy's Law is named after one of the sweetest, bravest dogs I've ever known, and is a fitting tribute to all the victims of the cruel third-party puppy trade, both past and present."
But Paula Boyden, veterinary director at Dogs Trust, the UK's largest dog welfare charity, urged the government to go further.
She said: "We would like to see additional measures introduced to ensure the ban is as robust as possible.
"There is time before April 2020 for the government to consider regulation of re-homing organisations and sanctuaries, ensure full traceability of all puppies sold, and strengthening of the pet travel scheme."