More than 5,000 people have signed a petition calling for dogs to be allowed on the passenger decks of ferries after a pet died in a car during a crossing to Dover.

The three-year-old pug had been left in a car during the journey on Friday when temperatures reached more than 30C.

P&O said procedures had been followed correctly - the windows were open and the ship's ventilation was working properly.

The family, who are believed to be moving from Germany to England, were travelling on the Spirit of France which left Calais on Friday at 10.45am and arrived in Dover local time at 11.20am.

When the family returned to their vehicle after the hour-and-a-half journey, three-year-old pug Merlin was dead.

Now a petition has been set up to hold ferry companies to account - as it explains cross-Channel ferries do not allow owners to have their pets with them. Animals must remain in the vehicles.

The petition has been set up by Nina Gadson, who lives in Aldershot, and addressed to Defra and Elizabeth Truss, the new secretary of state for Environment, Food and Rural Affairs.

It read: "A friend's dog died on a cross channel ferry run by P&O due to heat exposure, they came down to their car after the 1.5 hour crossing to find one of their beloved pets dead, this is not an isolated incident.

"Defra says that: Whenever animals are transported, including journeys with pets, the law says that: 'No person shall transport any animal in a way which causes or is likely to cause injury or unnecessary suffering to that animal’, and yet, ferry companies are insisting that pets remain in cars on unventilated car decks.

“It would be an animal rights abuse for a person to leave their pet in their car on land for over an hour, so how can the ferry companies be allowed to make pet owners do this?"

A P&O spokesman said: "We are reviewing our policy regarding the carriage of pets following the death of a Pug on board one of our ships on Friday.

"Temperatures ashore were oppressively hot and humid last week, leading to heat-stress health alerts from weather forecasters and medical authorities. However, coastal temperatures were considerably below those inland, and in the English Channel lower again due to the cooling effects of low sea temperatures.

"On the ship concerned, ventilation of the deck where the vehicle concerned was parked is excellent with a constant through-flow of cooling fresh air along the entire length of the deck. The deck is not exposed to the sun’s rays and our staff always respond positively to requests from pet owners to check on their animals during the crossings.

"Many airlines refuse to transport certain breeds of dogs, notably Pugs, Bulldogs and other brachycephalic breeds, due to the respiratory issues from which these animals are prone to suffer. P&O Ferries, which carries more than 50,000 pet dogs a year of all breeds, is reluctant to stop offering a service to the owners of certain breeds, believing that owners are best placed to judge the suitability of conditions when transporting their animals. However, the company is now reviewing its policy.

"This was a hugely distressing incident for the family concerned and for our personnel, who tried to revive the animal for 20 minutes, administering cardiopulmonary resuscitation and oxygen. The family has the company’s sincere sympathies.”