The Prime Minister, a dog lover since childhood, wants a new law that will ensure a puppy cannot be sold without the buyer being shown its mother and enforce strict new advertising regulations for canine sales online.
Her initiative, being worked on by Environment Secretary Michael Gove, follows a long-running campaign by MPs to raise ethical standards in the pet trade.
It comes as many families contemplate buying new-born puppies as Christmas presents for their children.
Mrs May last night declared her desire to “eradicate animal cruelty” from British society.
Any unscrupulous treatment of animals is disturbing
She said: “Any unscrupulous treatment of animals is disturbing – so in our drive to achieve the highest animal welfare standards in the world, we continually look at what more can be done.
“The arrival of a happy, healthy puppy, as I know myself, is a memorable time for a family – but it’s absolutely right we do everything we can to eradicate animal cruelty from our society.
“The proposals my Government is developing will be an important step forward.”
An estimated 700,000 puppies are sold in the UK every year. But concern is growing that tens of thousands of the animals are mass produced in farms where they can be separated from their mothers too early, kept in cruel and unhygienic conditions and transported long distances for sale.
Theresa May is to launch a crackdown on unscrupulous dog breeders
Measures being studied by Mr Gove to tackle the problem include ensuring that licensed dog breeders must show their puppies alongside the animals’ mothers before a sale is agreed.
Tighter regulations are planned so that sales are completed in the presence of the new owner in a drive to stamp out online purchases where the animal has not been seen first.
Licensed dog breeders are expected to be restricted to only selling puppies where they have overseen the breeding themselves.
And tougher advertising regulations are being drawn up that will apply to the online trade that will force sellers to display their licence number and the country of origin of any animals sold.
Legislation to enforce the proposals could be introduced into Parliament early in the New Year, according to Whitehall officials.
Environment Secretary Michael Gove is studying measures to tackle the problem
Ministers will also study new measures to tackle unethical and cruel puppy smuggling over national borders.
And they want to investigate how to prevent the breeding of puppies with severe genetic disorders.
Possible penalties for lawbreakers are still under discussion.
Mr Gove said: “At this time of year, it is all too easy to be moved by images online or adverts in the local press advertising new-born puppies looking for a home for Christmas.
“But what we don’t see is all too often a sad history of mistreatment and malpractice.
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“That is why we are looking at how we can go further to crack down on unscrupulous breeders so pet owners will have no doubt their new dogs have had the right start in life.”
He added: “This is one part of our efforts to ensure we have the highest animal standards in the world.
“We have also ensured CCTV cameras will be mandatory in all slaughterhouses and will increase prison sentences from six months to five years for animal abusers.”
MPs have called in Parliament for the introduction of a “Lucy’s Law”, named after a cavalier spaniel rescued from a puppy farm cage, that will make it illegal to sell a puppy without its mother being present.
Mr Gove is a dog lover whose pet bichon frise Snowy was a runner up in this year’s Westminster Dog of the Year competition.
And Mrs May has spoken fondly of how she grew up with dogs in her parental home.
She has said: “We always had dogs at home rather than cats.”
When she was a youngster, her family owned a poodle called Tassle and later a rescued mongrel called Lucky.
The planned crackdown follows a decision by senior Tories to highlight the party’s commitment to animal welfare issues.
Polling research showed that a pledge to have a free vote on lifting the ban on foxhunting with dogs repelled many urban voters.
Measures include a ban on the sale of puppies, kittens and rabbits aged under eight weeks
Mr Gove was also furious about a recent internet backlash against the Tories based on misinformation about their stance in a recent animal welfare debate.
The RSPCA has seen a 132% rise in the number of complaints about back-street puppy farming over the last five years.
Some gangs are thought to make up to £35,000 a week selling fashionable breeds and designer crossbreeds.
Officials confirmed last night that the Government will also press ahead with proposals floated earlier this year to raise breeding standards of pets in general.
Measures include a ban on the sale of puppies, kittens and rabbits aged under eight weeks and compulsory licences for anyone involved in breeding and selling dogs.