Fast-track surgery at a new centre in Auckland will be carried out by doctors paid thousands of dollars more than other specialists.
A doctors' union says the dedicated elective surgery centre at North Shore Hospital risks becoming a private monopoly.
The Association of Salaried Medical Specialists says private contractors could be paid more than $7000 a day for performing knee and hip replacements.
The association's executive director, Ian Powell, says Waitemata District Health Board has effectively chosen to run the centre like a private hospital, unlike the dedicated elective centre in Counties Manakau.
The director of the elective surgery centre, Dr John Cullen, says such payments are being reviewed.
He says remuneration is higher to reflect extra responsibilities surgeons will have for patients before and after operations, and to compete with what they could earn in private practice.
Dr Cullen says the centre will still carry out operations for 80% of the national standard price because of lower overheads and higher productivity.