A mother, her two children and dog have died in a house fire in the UK while her husband is fighting for life in hospital, unaware he has lost his immediate family.

Justine Collison, 33, and her eight-year-old daughter, Isabella, died when the blaze tore through their home in Collingham, Nottinghamshire, on December 15.

Mrs Collison’s son, Harvey, 5, and husband, Gavin, 34, were rescued from the burning home.

Justine Collison and her daughter died in the fire while her son died the next day in hospital. (Facebook)

Gavin Collison is unaware his wife and two children have died in a house fire. (Facebook)

However, Harvey died the following day in hospital where Mr Collison currently remains in a critical condition.

He has not woken up to be told his wife and two children have died.

The family’s dog also died in the house fire.

It is understood the fire may have started from a Christmas tree inside the home.

A photo of Isabella and Harvey Collison posted on social media just three days before the fire. (Facebook)

More than $40,000 has been raised to pay for the funerals after a crowd-funding page was set up.

“We are totally blown away by everyone’s kindness,” relative Lisa Bell wrote on the page.

“'We are heartbroken beyond words and are sending our love to Gavin's family and Justine's dad Gerald and his family and everyone else who has been shocked and affected by this horrible nightmare.

“Any funds raised will go to her husband and her mum to help pay for the funeral costs and to support the family. Anything that anyone can donate will be much appreciated.”