Using taxation to fund the government's national health plan was "only a possibility", the Department of Health said on Monday.

"[Taxation is] one of the possibilities, but it does not forego other possibilities," said health spokesperson Fidel Radebe.

Earlier in the day, Health Minister Aaron Motsoaledi told the SABC that funding for the National Health Insurance (NHI) programme could come from taxation.

"Those of us who earn better, pay more tax. All government functions work like that. I don't know another and I don't know why they must exclude this particular one," said Motsoaledi.

"What the Minister said is correct, that's one of the possibilities," said Radebe.

He did not know what the other possibilities were or provide any other details of a preliminary report on the NHI due to be released Wednesday.

The Democratic Alliance (DA) has criticised what it calls a lack of "public and transparent discussion" on the matter.

"As things stand, it appears that the African National Congress (ANC) is trying to force through its implementation by avoiding public debate on the matter," said DA health spokesperson Mike Waters in a statement.

"There are no Parliamentary health committee meetings scheduled yet to discuss this. There must be more room for public input."

Waters accused the ANC of making NHI policy "covered in a cloak of secrecy" and without consulting experts.

"We don't think those allegations are correct," said Radebe.

He said that the plan for the NHI would go through several stages and would, in due course, be available for public and Parliamentary comment.

"What the Minister [Motsoaledi] is saying, is people should not get worried at this stage," said Radebe.

"People are very mindful, and we don't want to cut corners on consultation."

On Friday, the Hospital Association of South Africa issued a statement saying that health economist Alex van den Heever had told its conference that the system was a "completely unworkable, unaffordable solution that won't improve health services, despite massive increases in expenditure".

Van den Heever said one of the proposals made in the yet-to-be released document, compiled by the ANC task team researching the matter, would increase the health budget by R100-billion.

"The danger is, that there seems to be an attempt to avoid debate on this issue," he said.

"The documents have been produced, but have not been subjected to external peer review or technical analysis," Van den Heever was quoted as telling conference delegates.

Waters described Van den Heever as "being part of the process".

Radebe would not say specifically whether the health economist had been a part of the NHI policy planning, but confirmed that many experts in fields related to health policy had been consulted.

"When this sort of work gets done, people you see are experts... There may have been people consulted, that is part of the process."

The ANC attacked critics of its health plan on Monday and vowed to continue its efforts.

"We will transform healthcare in South Africa and will not be deterred by narrow interest groups and individuals bent on undermining the introduction of the NHI before its work is made public," ANC spokesperson Jessie Duarte said in a statement.

Duarte said the accusations of critics such as Van den Heever were without substance.

"Unsubstantiated claims of an NHI 'secret report' and 'non consultative' approach of the NHI task team are untrue and only seek to create public confusion," she said.

The ANC was going through an "internal process" on the NHI policy and would only make public statements once it was concluded, said Duarte.