The RSPCA has slammed the state government's "last-minute" amendments to the animal welfare breeding code and accused it of backflipping on key policies designed to stamp out illegal puppy farms.

RSPCA Victoria CEO Maria Mercurio said that on Friday the organisation received an email from the Victorian government outlining "last-minute and furtive changes to the Breeding and Rearing Code of Practice".

In the email, it was stated that "sufficiently healthy bitches now have the potential to continue breeding after their fifth litter, but only if an annual breeding clearance certificate for each individual bitch is obtained from a veterinary practitioner".

Ms Mercurio said the RSPCA was "extremely disappointed" to see the changes, which she said "no longer limits the number of litters a female dog can have".

"The code that we thought was coming into effect limited the number of litters to five ... which is the key element in stamping out puppy farms," she told Fairfax Media.

"Otherwise, we end up back just where we started – with dogs that are confined for their entire lives and used as breeding machines."

She said that allowing a veterinarian practitioner to certify that a female dog was fit to continue breeding after five litters "fails dismally to protect the welfare of female breeding dogs and perpetuates puppy factory conditions".

"How fitness for breeding is determined by the vet is completely subjective, and does not guarantee that the long-term physical and mental health of the dogs."

But national president of the Australian Veterinary Association, Dr Ben Gardiner, said he was not aware of any "scientific research that says that after dogs have five litters, they are automatically unhealthy".

"This is a reasonable change from the government," he told Fairfax Media. "I'm very confident that vets could . . . make a valid decision."

The state government's two-year review of its code of practice followed a pre-election promise to crackdown on illegal puppy farms and animal abuse.