Untaken leave is contributing about $2 million to multimillion-dollar deficits at the Otago District Health Board, where more than 230 staff are owed six weeks leave or longer.
Of those, 34 doctors have accrued more than seven weeks of leave.
One doctor is owed about 700 hours and "a few up around 500 hours".
Chief operating officer Vivian Blake said leave accrual was a liability for the board.
"Every time you get a MECA [multi-employer collective agreement] settlement and there is a 4% increase in salary, whatever leave is there, such as 700 hours, that increases also by 4%."
In health services, where there might only be two specialists, it could be "very difficult" for doctors to go on holiday.
"The remaining specialist has to do all of the call, all of the surgery - everything that two would normally do, so it is a huge strain on the remaining clinician."
The board was looking at ways of addressing the problem, such as employing locums, which cost more, or working together with other district health boards to share the load in areas where there were a small number of clinical staff covering a specialty.
At last week's hospital advisory committee meeting, senior managers were told the problem of untaken leave had been building for several years and the issue needed to be addressed.
"The leave issue is now critical to our ability to meet budget," committee chairman Richard Thomson said.
"This is something management has got to get their heads around."
This is not the first time managers have come under fire about leave build-up and earlier this month Mrs Blake told the board it was a "near impossibility" to increase staff leave at the same time as focusing on the volume of work done.
She told the board it would need to decide where its priorities lay.
Mr Thomson said it appeared as though more staff had been working through January than were needed for the amount of activity undertaken at the hospital and there had been a missed opportunity to get people to take leave.
He realised management could not force people to take leave when they wanted them to, but perhaps they had to try a bit harder, he said.
The board had more than $1 million of untaken leave owing to staff and revaluation of leave following renegotiation of multi-employer collective agreements had added another $1.1 million.
"If we can't deal with that leave issue, next year it is going to be $3 million in the hole."
