Ally Stapleton, 49, originally saw the advert for the Chihuahua Shih Tzu cross online and now suspects the 10-month-old dog was farmed.

Her eight-year-old son was desperate for a dog and so she decided to go to Bury St Edmunds and pay the £200 asking price.

It soon became clear the dog had cherry eye, a disorder that if left untreated can result in inflammation, infection and blindness.

Mrs Stapleton took the dog, Pippa, to the vet to be neutered and to have the cherry eye treated.

However, the vet revealed that Pippa had much greater problems - the arteries to her heart were found to be blocked.

In order to save Pippa's life, she needs a balloon valve implant, costing £3,500 plus consultation fees.

Mrs Stapleton did not get Pippa insured as her previous insurers never offered to pay out for her last dog's treatments.

Now, Mrs Stapleton faces a heart-breaking dilemma.

Her son Danny has developed a strong bond with Pippa, who Mrs Stapleton says is happy and settled at their home. Yet, she cannot afford to pay for the surgery and Pippa suffers from fatigue, a jumpy heart and loss of appetite.

PACT Animal Sanctuary has offered to pay for the surgery. However, it will not return Pippa to the family in this scenario.

Chris Rockingham, founder of PACT, said returning Pippa to Mrs Stapleton would be going against the rules of the charity commission.

She said: 'The best thing for the dog would be for her to be handed over to a reputable shelter before finding her a suitable foster home.

'Pippa will require considerable after care and expert treatment, which will be costly, and no insurer will now cover her heart condition.

'If Pippa was handed over to us we would cover the costs of her surgery and any future treatment.

'We are not here to pay people's veterinary bills, we are here to help suffering animals.'

The RSPCA has offered to contribute £350 towards the surgery. However, this is less than 10pc of what Mrs Stapleton needs to prevent her son and Pippa from being separated.

Mrs Stapleton said she could not bear the thought of letting Pippa go.

She said: 'If I let her go, I will think about where she ended up all my life. The worst bit about all of this is my little boy.

'I've tried so hard to explain to him that she's got a bad heart, because all they want to do is play but the vet say she needs to be kept calm. He will be absolutely devastated if we lose her. It has changed his life having this dog, but the vet says she could die any minute.'

The seller of the dog has refused to explain how she acquired Pippa.

If you would like to donate money towards the surgery, please visit Mrs Stapleton's fundraising page.

GOVERNMENT ANNOUNCES CRACKDOWN ON PUPPY FARMERS

The government has announced stricter regulations around breeding and selling puppies as the RSPCA announces its busiest year investigating complaints relating to the puppy trade.Can you still d

Under the new rules, puppies bred by licensed breeders will have better protection, while any individual selling a puppy, including online, will need to get a licence. Furthermore, buyers will need to see the puppy with the mother at the place it was bred in order to complete a purchase.

Michael Ward, chief executive at the RSPCA, welcomed the tightening of regulations.

He said: 'This year our inspectors rescued hundreds of puppies and breeding dogs being kept in squalid conditions by heartless people cashing in on the growing market. We hope these proposed licensing conditions will improve the welfare of puppies and their parents and crackdown on the illegal trade.'