A family believe a venomous snake bit, and almost killed, their pet dog in their back garden.

Sarah Martin, from Stockham Park, Wantage, found three-year-old black Labrador Porter vomiting, shaking and foaming at the mouth.

A vet later found a suspected adder bite and a lump the size of a tennis ball on his rear leg.

The incident, earlier this month, cost the family £600 in vet bills.

Mrs Martin, 40, said: “What was really scary was that it happened in the back garden.”

Her husband Jason, pictured with his son, Jake, and Porter, warned people in the area to take care, adding: “If a child was ever bitten, I would hate to be the parent to go through that.”

Adders are the only venomous snake native to the UK. They are uncommon and are usually found away from human habitation.

Christine Sanders, of the Brook Veterinary Surgery in Steventon, is convinced Porter was bitten by an adder. She said: “It could potentially have been fatal.”

The Health Protection Agency this week warned walkers about the danger from snakes in the summer.