Up to 450 hospital consultants are entitled to a year's "holiday" with full pay before retiring, it was confirmed yesterday.
The perk was written into a contract signed by consultants in 1997 and allows them take the year off before their retirement while still earning their salary.
The year's paid leave was agreed before the contract was signed as a means of compensating doctors who had not taken all of their leave days before retiring.
The senior doctor is free to take the year off while the hospital where they work hires a stand-in locum medic to do their work.
However, it is so generous it allows the doctor to take the full year of "rest days" while also acting as their own stand-in.
It means that the consultant earns double pay -- their own salary plus the wages of the locum.
The Health Service Executive (HSE) confirmed last night that it was now trying to abolish this and other historical work practices.
A spokeswoman said: "In order to deliver greater efficiencies in these extremely challenging times, the HSE continues to examine historical work practices with all of its stakeholders, trade union bodies and representative associations."
It is estimated that if all eligible hospital consultants availed of the entitlement it could cost in the region of €100m between now and 2027.
That would be the year when the last of the consultants who are still on the 1997 contract would retire.
There are more than 2,200 hospital consultants in the public system. Those who signed a new contract in 2008 are not entitled to the measure.
However, around 450 doctors remain on the old contract and are on average salaries of €230,000.
The Irish Hospital Consultants' Association said last night: "This has been in place since 1998 to recognise the work that hospital consultants did at weekends in earlier years without any compensation.
"In the vast majority of cases, the compensation accepted did not match the amount of weekends actually worked."
The HSE wants hospital consultants to change their rosters and be more available in hospitals in order to extend the working day.
Last month FAS staff announced they were going to the Labour Court to protect their right to pre-retirement leave of up to 44 extra days.
Under the leave scheme, staff can get up to 44 extra annual leave days in the two years before their retirement.