The Irish Medical Organisation has accused the Government of misleading the public by describing their proposed health insurance reforms as a type of universal health care.
In its detailed response to the Government's recent White Paper on Universal Health Insurance, the IMO said the proposals are simply a reform of the financing of health care, not a commitment to a more equitable system of health care.
The union's president, Professor Trevor Duffy, said the plan would lead to extra payments by many people to cover services that are currently financed through the taxation system.
He said many people who are currently paying for private health insurance would have to continue to pay but would lose access to the benefits they currently enjoy.
Meanwhile, the chief executive of the Mater Private Hospital has warned that the "exodus" from the private health insurance market will lead to hospital closures and could push public services to "tipping point".
Fergus Clancy said the large numbers giving up their health insurance policies represents a "significant time bomb" for the public health services.
Around 300,000 people have given up their private policies since 2008.
Mr Clancy said if the trend continues, he predicts more hospital closures within the next 24 months following the closure of Mount Carmel hospital in Dublin.
Speaking on RTÉ's Today with Sean O'Rourke, he said public health services could then reach "a critical tipping point" where those who no longer have private health plans join public waiting lists.
Mr Clancy suggested the Health Service Executive should charge health insurers less to use public beds for private patients to reduce costs for private insurance customers.
He said private hospitals had reduced costs for insurers by 7% but costs had risen for insurers to access public beds.
People need to stay in the private health insurance market to ease numbers accessing overstretched public health services, he said.
Mr Clancy said that while the Universal Health Insurance plans are "admirable", implementation by 2019 is "beyond challenging".