A dog described as the "saddest in the world" could be put down after a second family returned her to the Toronto shelter they adopted her from a year ago.

Lana the Labrador-cross was given her nickname in 2015, when a photograph of her looking dejected in her kennel after being abandoned by her first family went viral.

More than 4,000 people applied to adopt the dog and the centre received $15,000 (£8,500) in donations - but unfortunately it did not work out with the family staff selected for Lana and she now faces being put to sleep six days after her third birthday.

Lana was first returned to the the Canadian non profit Rescue Dogs Match after displaying unexpected, aggressive “guarding behaviour” around food in 2015.

This time, staff suggested the family who adopted her no longer wanted her because she was not keen enough on being cuddled.

Staff said the kennel is now so overcrowded that if Lana is not re-homed by 20 May she could be euthanised.

“She has made some improvements but there is still work to be done,” the centre said in a Facebook post, explaining that Lana has complex needs and cannot live with other pets or children.

Lana was born a street dog in Mexico in 2014 and as the runt in a litter of ten she had to compete for food.

She was rescued and flown to Canada while she was still a tiny puppy but by then she was already showing possessive behaviour around food. The behaviour did not completely go away despite training.

After five months in foster care she was adopted by a family with children, but she soon snapped at the mother during feeding time.

The family returned her out of fear she would inadvertently harm one of the children.

After spending several months in boarding kennels while staff sifted through thousands of applications to adopt her, Lana was re-homed, this time with a family without children, who had significant experience with dogs.

Staff at the centre hoped this would be her "forever home", but unfortunately the family did not turn out to be the right fit and returned her a few months later.

"Lana's adoption did not work out because people want a dog they can pet and play with," Brenda Dobranski, the founder of Rescue Pets Match, told the Dodo. "Lana is a silly fun girl but she is not the kind of dog that will let you give belly rubs to and sleep in bed with. She loves to have a job."

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Ms Dobranski said the best environment for her would be on a horse or hobby farm "where she can be outside most of the time 'helping' her person with the chores around the property".

She said: "The best family for her would be a mature couple or person that has the time, patience, determination and commitment to help her become more confident. A family that would arrange controlled play dates with other dogs, without food or toys around. A family that has a routine she can rely on, and an active lifestyle that would banish the thought of endless hours in concrete bunkers with nothing to do."