Mr Matthew Checketts, consultant anaesthetist at Ninewells in Dundee, said he and some of his colleagues regularly work up to 18 hours without rest and are often on call for long periods.
He spoke out following the case of young doctor Lauren Connelly, 23, who was killed in a car crash while driving back from a night shift at Inverclyde Royal Hospital in September 2011.
He said the burden placed on consultants in many specialities meant they were at risk of fatigue despite having to make vital decisions about patient treatment.
Mr Checketts said: "Many of us are working very long hours. We have emergency duties and responsibilities for up to and beyond 24-hour periods when on call, and that is not good for individual doctors and not good for patients.
"It is not unusual for a consultant in one of the acute specialities like anaesthesia, surgery, or intensive care medicine to be working in the hospital with little or no rest breaks for 18 hours at a stretch - sometimes more.
"This is quite common and it's becoming more so because consultants are rightly far more involved in dealing with emergency patients during the night or weekends than they were 10 years ago.
He added: "Consultants are leading from the front and giving their all, but sometimes the result is that they are making very important decisions about patients when they are very tired."
Junior doctors are subject to strict rules set out by the European Working Time Directive that govern the hours they work, but some consultants opted out of a similar system that would have put limits on their workload.
Consultants can also be on call in busy specialities for 24 or even 48 hours, and, unlike the conditions applying to junior doctors' rotas, are not entitled to 11 hours' consecutive rest a day and breaks every six hours.
Mr Checketts said: "People get through it as best they can, usually by drinking black coffee and making the best of it. Your health and home life can suffer.
"Driving home after a very long stint on duty sometimes you realise you are not fit to drive and have to catch up on sleep in a lay-by. If you are too tired to drive, are you are too tired to do your job?
"This is not a staffing issue - it is not a numbers game, and it's not about money either. This is a problem with the pattern of work."
He said senior consultants had previously worked 120-hour weeks as junior doctors in the 1980s and "are prepared to put up with it." However, he added: "Younger consultants are not happy about it."
Dr Connelly's father, Brian Connelly, said: "The long working hours culture affects not only the health of medical professionals, but potentially those of the patients they are caring for."
Simon Barker, deputy chairman of the BMA's Scottish Consultants Committee, said health boards should work with doctors to make sure their shift patterns were safe and sustainable.
He said: "Where staff shortages occur, boards must ensure doctors are not expected to work when exhausted, to ensure the health and safety not only of the patients but also the doctors."
A Scottish Government spokesman said: "Consultant rotas are designed locally by consultant staff, and are designed to meet the limits of the Working Time Regulations. Working patterns should be flexible enough to respond to the unpredictable nature of providing medical care, while ensuring adequate rest periods are built in which keep staff well rested and safe for duty."