Dr Anna Gregor, who led the country's successful cancer strategy and was recognised for her services to medicine with a CBE, has never held political affiliations but said she felt compelled to speak out because she was concerned "unreasonable distress and panic" was being spread among patients.
The future of the NHS became a heated referendum topic after the comments of Scottish breast cancer Surgeon Dr Philippa Whitford went viral last month. Dr Whitford warned Scotland's NHS would wither away within a decade without a Yes vote.
In England, private companies can bid to run NHS services and the Yes campaign argue this could affect Scotland unless it leaves the UK.
But Dr Gregor, once listed as one of the most powerful women in Scotland, said: "I take a very dim view of clinical colleagues using our highly privileged position of trust with the patient population and the community to politically scaremonger."
Dr Gregor stressed that Scotland already has control over the NHS north of the Border. She said: "The health service is one of the pillars of the devolution settlement. Since 1999 we have had complete freedom about how we run the NHS in Scotland ... and we have demonstrated that. The Scottish way of doing things is distinctly different to that of England.
"The way that we have held onto our infrastructure while the English have introduced market forces and purchasers and providers - we have none of this in Scotland."
A Czech by birth, Dr Gregor has lived in Scotland since 1980 and calls the country her adopted home. She worked for the Scottish Government mapping the future of cancer services between 2001 and 2006, later becoming a leader of the respected patient safety programme. She said she did not agree with many English health service reforms and knew few who did.
But she also said it was illogical to regard any use of private enterprise in healthcare as "evil". Opticians and dentists are run by private firms in Scotland, she said, and waiting lists are kept down by sending patients to private hospitals for treatment.
With signs GP services are struggling to cope with the growing elderly population, she suggested Scotland should possibly consider whether private providers could help.
But Dr Gregor, a consultant oncologist for NHS Lothian who fully retired from clinical practice last year, added: "I think the idea that somehow we will get infected by private enterprise creeping over Hadrian's wall is disingenuous at least."
She dismissed arguments that use of the private sector by NHS England would result in Scotland having less money to spend on health, saying Scotland can choose how it uses its block grant.
Campaigners have "muddled" the way the private sector is involved in healthcare, she said, noting the NHS remains free for patients UK-wide even if some services are supplied by private firms.
She urged people not to worry about losing the NHS because Scotland is part of the UK, but instead to worry about how it will cope with the rising elderly population and advancing technology. The current healthcare set-up is unsustainable, she said, but referring indirectly to SNP decisions to save Ayr and Monkland hospitals when they were earmarked for closure, added: "We have for political reasons put the whole Scottish healthcare system into aspic."
Dr Gregor continued: "We must stop using currency of buildings and beds, which is an outdated, 19th-century concept -and allow the health service to work with patients and communities to create an NHS fit for the 21st century and beyond."
Dr Gregor, a member of Queen Margaret University court, stressed she was not speaking to promote No campaign Better Together. She said: "The thing that made me decide to talk about this subject is that both the politicians and, much to my chagrin, some of the clinicians are now scaremongering and telling the voters and patients that the only way to protect our NHS is to vote Yes. That is a total and utter lie."
Scottish Labour's health spokesman Neil Findlay described Dr Gregor's comments as "an incredibly important intervention into the debate over the future of the NHS".
A Scottish Government spokesperson said: "Under current funding arrangements, any cuts to the health budget in England through austerity, privatisation or patient charging will have a knock-on effect which cuts Scotland's budget. That is one of the reasons why the Scottish Government believes that our health service would be better protected under independence.
"We are committed to protecting the founding principles of the NHS and maintaining it as a publicly owned health service, free for everyone at the point of use. We believe there should be constitutional protection for the NHS in an independent Scotland - which would ensure that the NHS will be in public hands for generations to come."