Seven-month-old Tammy, a West Highland Terrier, sustained 90 per cent burns after jumping into the bath, and owner Helen Race was left heartbroken after vets at the PDSA said Tammy's injuries were so serious they would have to put her to sleep.
Mrs Race, 28, from Hylton Road, Sunderland, said: "My children have all been left shaken by what has happened. They were so upset they couldn't even go to school.
"This firework was thrown into our back garden and made such a noise that Tammy jumped into the bath I had been running for my boyfriend."
Mrs Race, who has three sons and two daughters, is calling for a ban on fireworks to prevent other animals suffering.
She said: "I had warned these kids about setting off fireworks at the back of my house, but they just laughed – then this goes and happens."
The RSPCA today condemned the attack and repeated its calls for a substantial reduction in the legal decibel limit for fireworks.
A spokeswoman said: "Under current laws, fireworks of 120 decibels can be legally sold – but they make the noise equivalent to a jumbo jet taking off.
"We want to see the law reduce this to at least 90 decibels, which is the same as someone slamming a car door.
"What has happened in this case is terrible and quite extreme. However, we have known for some time that fireworks do cause psychological damage to animals.
"Furthermore, they also lead to a number of pets being run over at the time of year. The frightened animals get such a shock that they dart into the roads and are knocked down."
New legislation makes it illegal for people to set fireworks off after 11pm.
However, Tyne and Wear's chief fire officer, Richard Bull, has called for a ban on the sale of fireworks.
His comments came just days after the death of Arthur Lonsdale, who died after a firework was pushed through the letterbox of his home in Westerham Close, Witherwack.


Toll of suffering

WORKERS from the RSPCA say they have been flooded with calls reporting incidents in which fireworks have either killed or badly injured animals. These include:
* A dog left so frightened by a firework that he bit through a wood door, leaving splinters in his gums.
* A dog so terrified that he ran away until the pads on his feet were red raw.
* Family pets who become lost, after fleeing miles from home because of fireworks being let off.
* Fire crackers being deliberately thrown into a field of horses to scare them.
* A firework tied to a rabbit and set off, killing the animal.
* A hamster being used as a cannonball after it was attached to a lit firework.