The family of 74-year-old Karl Andree have appealed to David Cameron to intervene after he was sentenced to 350 lashes for making his own wine.
Mr Andree has survived cancer three times and suffers from asthma, but his children fear that his frailty will cause the brutal punishment to kill him.
The oil executive was arrested in Jeddah last year after he broke the country’s strict anti-alcohol laws when police found homemade wine in his car.
Since his arrest he has been held in a notorious prison where he remains until officials carry out the lashings.
His 33-year-old son Simon told The Sun: “There is no doubt in our minds that 350 lashes will kill him.
“Our father has given 25 years of his working life to Saudi Arabia, and this is how he is treated.
“Until his arrest, he has always been happy working there and felt safe. He is 74, has had cancer three times and his wife is dying in a home in the UK.
“He now needs medical care for his cancer and asthma and there is no doubt in our mind that 350 lashes will kill him.
“We implore David Cameron to personally intervene and help get our father home.”
Simon later told the BBC’s Today Programme: “I feel that all the business dealings between Saudi Arabia and the UK are probably getting priority.
“All I can say is that the British government's primary responsibility is to its British citizens and he is a British citizen.
“I ask that the government plead for his clemency and for him to be released.”
Mr Andree’s grandchildren are reportedly ‘worried’ about their grandfather and asking if he is ‘out of jail yet’.
A foreign office spokesman said in a statement: “Our embassy staff are continuing to assist Mr Andree, including regular visits to check on his welfare, and frequent contact with his lawyer and family.
“Ministers and senior officials have raised Mr Andree's case with the Saudi government and we are actively seeking his release as soon as possible.”