The reality TV star was given Pomeranian pup Mr Chai Bear – imported from Russia – as a 21st birthday present by boyfriend Tommy Fury in May this year.
Hague, 21, has now told The Sun: “If we had our chance again, we wouldn’t have imported from Russia.
"The autopsy results showed that his skull wasn’t fully developed and he didn’t have a white blood cell left in his body.”
Sellers told the couple the specially-bred dog was healthy, but after he died an autopsy revealed he had been born with enlarged internal organs and part of his brain was exposed.
Hague added: “If we had the time again, we’d have a dog from the UK.”
The reality star announced Mr Chai Bear’s death on Instagram in June, saying, “Tommy and I are utterly heartbroken and shocked.”
Mr Chai Bear had his own Instagram page with 149k followers and Hague had described herself and boxer Fury, 21, as his parents.
The couple met when they were runners-up in the ITV2 dating show last summer.
The price of puppies more than doubled during the first coronavirus lockdown, with dogs costing an average of almost £1,900.
Animal welfare charities have expressed fears this could encourage smuggling, dog theft and “puppy farming”.
Watch: The coronavirus lockdown sparked a rising demand for puppies