Around 180,000 medical appointments were cancelled by hospitals in Northern Ireland last year, it was revealed.
Highly paid consultants, some on six figure salaries, were responsible for much of the disruption and enjoyed 55 days annual leave for holidays and study. They were also delayed by urgent work like operations, health service officials said.
Often patients were still treated, simply shifted to a different doctor or rescheduled in advance after administrators realised the consultant would not be available and cancelled their slot.
SDLP MLA Conall McDevitt said: "The issue is productivity. If you are not delivering the goods 40% of the time there is a problem. Consultants are as guilty of not delivering the goods as patients are of not turning up."
Many of the 182,815 cancelled appointments in 2011/12 were attributed to how statistics were recorded because switching doctors as the consultant was unavailable still counted as a cancellation, the health service said. Sometimes an intended appointment letter was not sent to the patient after civil servants realised the consultant would not be available.
Health and Social Care Board (HSCB) chief executive John Compton said: "Whether you are a senior clinician or junior clinician you have to seek permission for annual leave. Unfortunately life throws up circumstances where it is difficult not to approve annual leave but the notion that in some way there is casualness about annual leave is not correct."
Around 1.5 million appointments take place every year, with two-thirds involving patients with long-term health conditions. In 2011/12 patients missed 157,000 outpatient appointments and cancelled 184,000. Reasons for the consultant being unavailable included sickness or annual leave, study leave, the doctor retiring or delayed in theatre.
Northern Trust had the worst rate of cancellations and the Southern Trust the best, by a significant margin.
Mr Compton said often appointments were put back because of medical need or there were outstanding tests. He said health service users were offered flexibility in making appointments within a six-week window.
Sean Donaghy, Northern Trust chief executive, said: "Our attitude has focused on how long patients are waiting (for a first outpatient appointment), are we getting to the nine weeks target? The outcome would suggest that we are improving as far as that is concerned."