Asking district health board chief executives to submit letters of resignation would set a dangerous precedent across the public service, National's state services spokesman says.
Health Minister David Clark last week said he was seriously considering asking for the letters and then deciding which ones to accept.
He wants to make sure all the DHB chiefs agree with the government's health agenda.
National's Todd McClay is urging him not to do it.
"This sets an extremely dangerous precedent across the public service," he said on Monday.
"These people are leading large and complex organisations on behalf of the public - it's demeaning and insulting to require them to sign resignation letters without cause because the new health minister wants to show who's boss."