A premature baby penguin has been nursed back to health at London Zoo after her parents accidentally stepped on her egg and broke it.

The zoo says keepers were astonished to find that the female Humboldt penguin chick, nicknamed Rainbow, was still alive inside the broken egg. They rushed the chick to the zoo's clinic, where vets transferred her to an incubation chamber.

The chick spent weeks cuddling with a soft toy penguin and was fed what the zoo called "penguin milkshake": blended fish, vitamins and minerals.

Premature Penguin Saved: A penguin chick has arrived early at @ZSLlondonzoo after keepers discovered her egg had been accidentally crushed by other penguins. Little Rainbow weighed less than 100 grams and was rushed to a vet. Thankfully she ad is now thriving. #TenNews pic.twitter.com/7WfH8OqcAt

— TEN Eyewitness News (@channeltennews) July 19, 2018

Penguin keeper Suzi Hyde said on Thursday that the birds typically reject chicks when they accidentally step on their eggs.

She said the one-month-old chick is growing quickly, and that she will stay in the incubation chamber until she reaches 10 weeks.

AAP