Simon Bridges claims 10,000 patients will miss out on elective surgery this year.
The National Party leader says in the nine months to March, there were 6500 fewer surgeries than for the same period last year.
Bridges says the total number is almost certain to be higher with the five-day junior doctors' strike last month.
"This is a serious problem. These procedures include cancer, cardiac and neurosurgery operations, so they are more than minor."
He is calling on Health Minister David Clark to step up to ensure nobody dies while waiting for surgery.
"District Health Boards are currently 179 cardiac surgeries behind where they should be. It would be a tragedy if anyone was to die while waiting for an operation that should have been performed by now."
"On current projections more than 1800 fewer gynaecology procedures and 1500 fewer orthopaedic procedures will be performed by the year to June 30."
- Terminally ill man demands reform of New Zealand's cancer plan
- Three more DHBs used unsterilised equipment in surgery
Dr Clark admitted the strike would result in fewer surgeries being carried out, which is why he's been urging the district health boards and unions to sort out their differences.
"Addressing a decade of underfunding, and the erosion of pay and of conditions for our health workforces is not going to happen in one Budget or a single bargaining round, but we are making progress," he told NZME.
Dr Clark said his advice is that surgeries are running at about 98 percent of what was planned.
He also said therehave been data collection delays, and some minor procedures are now being carried out outside of surgical environments, both of which could contribute to numbers looking lower than expected.