Cape Town - The proposed national health insurance (NHI) might turn out to be unconstitutional, the Freedom Front Plus said on Monday.
This was because taxpayers would be forced to join and pay contributions, FF Plus spokesperson Anton Alberts said in a statement.
This was contrary to section 18 of the constitution which guarantees freedom of association.
"South African taxpayers are already heavily taxed and imposing a further tax in the current economic climate will further punish the working, middle class," he said.
However, last week's publication of the NHI green paper was welcomed by the SA Medical and Dental Practitioners Association (SAMDP).
"The NHI will improve coverage and the quality of services offered to South Africans irrespective of their ability to pay for it," the association said in a statement.
"We further support the phased introduction of the systems."
The SAMDP would study the document and provide a detailed response.
The majority of SAMDP doctors provided services in areas where communities were poor and could not afford private healthcare, it said.
The SAMDP would support government in preparing doctors to make a success of NHI.
"We applaud government for taking this initiative.
"The critics of NHI conveniently forget that South Africa's life expectancy is about 48 years. Doing nothing about this is more harmful," it said.