Oscar-winning filmmaker Oliver Stone has written to the Ministry of Defence to protest against the "barbaric and shameful" use of live pigs to train British Army doctors.
The American director, producer and screenwriter of films such as JFK, Born On The Fourth Of July and Wall Street, is a veteran of war himself.
He urged Defence Secretary Philip Hammond to put an end to British participation in the "cruel" drills.
Oliver Stone has hit out over the 'cruel' operations performed on live pigs
It comes after Gideon Raff, the creator of hit TV series Homeland, also wrote to Mr Hammond last week calling on him to switch to more "humane and effective" practices.
Formerly known as Operation Danish Bacon, the training sees the pigs shot with high-powered rifles and then operated on at a course provided in Nato facilities in Jaegerspris, Denmark.
In a letter addressed directly to Mr Hammond via email, Stone said: "Pigs are very intelligent beings - just like the dogs and cats with whom millions of us share our homes.
"Using them as targets and cutting them apart is barbaric and shameful."
The MoD last month stood by its participation in the drills, claiming they helped save lives on the battlefield.
A spokeswoman said that by taking part in the Danish exercises rather than replicating them in the UK, it was minimising the number of animals involved.
But in his letter, Stone backed a call by animal rights group People for the Ethical Treatment of Animals (Peta) for the use of lifelike dolls that "breathe" and "bleed" to replace live animals.
He argued that a combination of simulators and clinical experience had been shown to be more effective, and that the training went against UK animal welfare regulations.
"It is unscrupulous and underhanded for the MoD to outsource this unnecessary cruelty knowing full well that it would not be allowed on British soil," he said.
"The brave men and women who risk their lives to fight for our countries deserve the best possible training, and sending soldiers to participate in reprehensible exercises that inflict severe pain on pigs does not improve the preparedness of the UK's military medical teams.
"Please do not condone cruelty to animals by forcing soldiers to engage in such barbarism."
Stone, who served in the US infantry during the Vietnam war, has won three Oscars for his work on Platoon, Born On The Fourth Of July and Midnight Express.Suggest a correction