The family's four-bedroom home in Thetford, Norfolk, flooded on May 23 after one of the toilet's flush system broke and got stuck overnight.

Mother-of-three Emmaline Green, 46, asked the builders to move the family pets, including daughter Beatrix's beloved Mr Big Fish, to the carport before drying out the home.

But instead the builders just moved the tank into a bedroom and switched on eight humidifiers, raising the home's temperature to 122F (50C), Dr Green told The Sun.

On May 31 GP Dr Green reported to insurance company Royal Sun Alliance, which had commissioned the builders, that the house was too hot.

But on June 3 she and her fiancé, veteran soldier Hadrian Holland, 33, found the pets, Good, Bad, Ugly, Darth Vader and Mr Big Fish floating lifelessly in the tank.

Dr Green added that the excessive heat also started small fires in kitchen drawers, broke their TV, warped furniture and melted candles.

She said: “We found the fish just floating in their tank. They didn't stand a chance.

“The one that broke my daughter’s heart was Mr Big Fish. He wasn’t just a fish to her, he was a friend.

“We had him for six years after she won him at a fairground. I sat her down and told her in the garden and she just wept and wept.”

She added that the family will never forgive the builders for what they did or 'for how they've treated us'.

The family are currently staying in a caravan while the house is being repaired and Dr Green says the ordeal has so far cost them £7,000.

A spokesman for Royal Sun Alliance insurance said: “We’re very sorry for the problems Dr Green and her family have experienced with this claim. It is a complex claim with multiple parties involved, but the way it has been handled falls below the standards our customers expect of us and those we set ourselves. 

“We have taken steps to expedite this claim to ensure it is satisfactorily resolved, while also looking to learn from this case. A formal complaint has been finalised and we have offered Dr Green compensation for the disruption caused.”