Unions have called on assembly public spending watchdogs to investigate the building of two £40 million health centres in partnership with private business in Northern Ireland.
Unison accused health minister Edwin Poots of trying to create a two-tier service and claimed the latest development threatened the future of Lagan Valley and Daisy Hill Hospitals.
The new centres in Lisburn and Newry will accommodate GPs and community services, said the health department.
Unison regional secretary Patricia McKeown said: "It is now time for the public accounts committee and the assembly health committee to move to investigate before irreparable damage is done to our health and social care system."
The centres will be financed through a mechanism known as Third Party Development (3PD), which involves a partnership arrangement with a private sector company. They will serve as hubs providing health services, including GPs, diagnostic, imaging and children's. Physiotherapy, podiatry, older people services and mental health care are also expected to be available.
The procurement process is expected to start shortly, with completion of the facilities anticipated in 2016. The developments will allow more people to be diagnosed and treated in the community, closer to home. Under plans to transform how local care is delivered, people will be expected to attend their local health centre more as opposed to the local hospital, which is more expensive to run and often difficult for older people to access.
Ms McKeown said there had been a startling growth in private medicine funded out of the health service budget. She said: "This is the slippery slope. The public are continually told that services or hospitals must close or be centralised for medical safety or because we do not have enough doctors. But the same doctors are receiving second payments to treat our patients privately.
"Our NHS facilities are being opened up to private companies. NHS patients are being displaced in favour of those who can pay and the nature of the contracts with the private sector is not open to public scrutiny."
The two health centres are to be built using private sector funding but will be equipped and staffed by the NHS. Ms McKeown said: "Unison has been consistently warning of the dangers of this growing privatisation and the threat it poses to our health care system. It is now time for the Government watchdogs to act."
Health minister Edwin Poots defended the move. he said: "A key element of ongoing healthcare reform is the need to move services away from hospitals except where it is absolutely necessary and to develop service provision in the community so that people can access treatment closer to their own homes or, where possible, at home. The provision of these new facilities will assist that process."