Police forces have warned private ambulance drivers they will be prosecuted if they do not switch off their blue lights - even in emergencies.
Lothian police have been accused of endangering lives after they told private ambulance company Lifeline their employees would be taken to court if they are caught with their lights on at the East Lothian border.
Dave Cooper, operations manager at Lifeline, called the threats "ridiculous".
"It may seem dramatic but this could actually kill someone. Our ambulance drivers have permission to exceed the speed limit if necessary as it could mean the difference between life and death.
"If an organ is out of the body for too long then it deteriorates, so it is really important to get them delivered as quickly as possible."
Lifeline is a private company which transports blood for transfusions and organs for transplants. Although its vehicles are formally recognised by the DVLA as ambulances, Lothian police are refusing make exceptions.
Cooper says the difficulty arises when drivers are travelling along the A1.
"There is a single carriageway for most of the way so you have to make up time when you can and the safest place to do this is on the dual carriageway."
The warning was issued by the Lothian and Borders Police after an ambulance driver was been fined as he sped to hospital to deliver a kidney for a life-saving transplant.
As he had his blue lights flashing, Thomson expected his fine to be waived but was handed a £60 fine and given three penalty points on his licence.
Thomson, who drives private ambulances for Lifeline, had picked up the liver from Edinburgh's Royal Hospital for Sick Children when he was caught driving at 84mph on the 70mph road.
Lifeline, who disputed the fine, were told private ambulances do not fall under the Lothian and Borders Police's definition of an emergency vehicle.
Cooper added Thomson's speed "was not even excessive speeding".
A spokesman for Lothian and Borders Police said: "Lothian and Borders Police Road Policing Unit work closely with the NHS to establish the authenticity and credibility of any agency claiming to be carrying out work on their behalf when caught speeding.
"The decision to prosecute a driver for any motoring offence is made by the Procurator Fiscal."
Suggested For You
Get top stories and blog posts emailed to me each day. Newsletters may offer personalized content or advertisements. Learn more