Four official photographs marking Prince George's third birthday have been released by the Duke and Duchess of Cambridge.

The images show the prince at the family's Norfolk home, Anmer Hall, and were taken in mid-July by photographer Matt Porteous.

One image shows the prince playing with the family dog Lupo.

Prince George Alexander Louis - known as His Royal Highness Prince George of Cambridge - was born on 22 July 2013.

A Kensington Palace spokesman said: "The Duke and Duchess hope that people will enjoy seeing these new photographs.

"They would like to thank everyone for all the lovely messages they have received as Prince George celebrates his third birthday."

However, the RSPCA has criticised the picture of Prince George holding an ice cream close to the mouth of the family dog.

'Difficult to digest'

"It is lovely that Prince George is trying to help keep his family dog, Lupo, cool in these high temperatures," a spokesman said.

"We would advise people to be cautious when giving their dogs food meant for human consumption as some items, like chocolate, can be highly toxic to dogs and dairy items can be difficult for them to digest.

"Instead of ice cream we would suggest making an ice lolly from pet-friendly ingredients. Making these can be really fun for children and the end product is both safe and enjoyable for dogs."

Paula Boyden, veterinary director at the Dogs Trust charity, agreed.

She said she "would always advocate seeking methods to keep your dog cool, but possibly not in the form of an ice cream, unless it is a dog-friendly version".

"The cow's milk and sugar content in ice cream can sometimes lead to digestive issues. Whenever you do treat your dog, do consider the ingredients and always seek the advice of your vet," she added.