Dozens of nursing and doctors' posts in Northern Ireland remain unfilled.
There are not enough staff for the elderly, the mentally ill and those with learning disabilities, an Assembly debate said yesterday.
There are 74 long-term nursing vacancies and 82 doctors sought, Alex Easton (DUP, North Down) said.
"It is extremely serious that we don't have enough doctors in Northern Ireland," he said.
"I find it incomprehensible that in 2008 some £13 million was spent on agency staff, we can and must do better."
Vacancy levels remain less than 3% and have been falling.
Mr Easton was debating a motion noting the number of unfilled positions in the health service and called on Health Minister Michael McGimpsey (UUP, South Belfast) to review urgently how his department recruits.
Hundreds of positions across Northern Ireland remain empty, partly because of difficulty finding people with very specialist skills.
Claire McGill (Sinn Fein, west Tyrone) said: "These are the people that are most vulnerable, these are the groups within our community that we repeatedly say that we care about.
"In terms of the elderly, mental health and learning disability the vacancies are particularly marked and particularly acute."
The minister said everybody within the Executive voted for the 3% efficiency savings which he was bound by.
"There will be no cuts in front line services, there will be changes to the way services are currently delivered," he added.
He said money saved through greater efficiency would be ploughed back into services.
The rate of vacancies has almost halved and stands at 2.4%.
In March 2008 there were 1,266 whole-time vacancies.
He defended the use of agency nurses to cover maternity vacancies.
"I want to ensure staff and patients are part of the 21st century service that is fit for purpose."