This week, the Southern District Health Board said it was consulting staff on a proposal to relinquish its contract with the National Screening Unit to provide the service for Otago and Southland women.
Health boards and private providers contract with the National Screening Unit to run regional services. Outside Otago and Southland, South Island breast-screening is provided privately, but in the North Island, it is run almost entirely by health boards.
Prof Cox said the most robust overseas screening programmes were in public hands.
New Zealand's regionalised health system did not suit public health initiatives like screening, which worked best on a large scale.
Private providers were capable of running the services, but as more areas privatised and the system became more fragmented, the goal of a strong standardised service became harder to achieve.
''I think [privatisation] is of concern; it's important it doesn't jeopardise the effectiveness of the programme.''
Ministry of Health national services purchasing director Jill Lane yesterday said the National Screening Unit was concerned about the long-term viability of the southern service.
The unit had worked closely with the Southern District Health Board to address problems, including a lack of specialist staff who could work to its required standard.
''To ensure the quality, reliability and sustainability of the service, the radiology team in BreastScreen Counties Manukau DHB has been supporting the service, but this is an interim arrangement.
''The [Southern] DHB and NSU share common concerns about the long-term sustainability of the service, given the workload pressures on the small breast-screening team, and particularly on how to ensure women can continue to have confidence in the services they receive.''
The board will announce its decision to staff on October 8.
