Otago University senior clinical lecturer Dr Erik Monasterio, one of the co-lead authors of the letter, claimed the agreement threatened governmental ability to deliver affordable health care and legislate to protect public health and reduce health inequities.
"And all the while, the text is shrouded in secrecy," he said.
"The negotiations are not about the way most of us think of trade — you and me buying and selling things.
"Instead they are protecting the massive investment profits of multinational companies that are bigger than the whole New Zealand economy."
Dr Monasterio described the TPP as "an unprecedented expansion" of intellectual property rights that would "push up the cost of affordable and life-saving medicines, hitting hardest the already vulnerable households in New Zealand and other countries such as Vietnam and Malaysia".
He also feared governments could be sued for protecting health — but governments cannot sue back.
"This will stop important health initiatives on tobacco, alcohol, the obesity epidemic, climate change, antibiotic resistance, and other major future challenges," he said.
"We are asking for heath impact assessments, for each nation, and then their public release, so that parliaments and the public can discuss the issues — before political tradeoffs are made and the agreement is signed."
The NZNO today released a statement claiming there was potential for the drug-buying Pharmac model to be undermined, and for an extension on length of time for patents impacting on the affordability and access to medicines.
Mr Groser said while the Government recognised the strong interest many had in the TTP, negotiators were working to get the best deal for Kiwis.
"The Government's view is that objective wouldn't be advanced by publicly declaring New Zealand's hand to our negotiating partners," he said.
TPP participants had also agreed to maintain the confidentiality of the negotiating texts, which was a standard practice in free trade agreement negotiations, he said.
"The Government has been consistently clear that New Zealand won't negotiate — in TPP or any other trade negotiation — on the fundamentals of the public health system."
The Ministry of Foreign Affairs and Trade states the agreement would deepen economic ties between the agreement's diverse members by opening up trade in goods and services, boosting investment flows, and promoting closer links across a range of economic policy and regulatory issues.
Stephen Jacobi, executive director of the New Zealand International Business Forum (NZIBF), told the Herald that the health professionals' concern were understandable and public debate about the merits of trade agreements was important.
"We support the call for more information to be made available about TPP, but we do not believe that the negotiating texts can be made public in advance of the ratification process."
The NZBIF did not believe or expect the provisions in the agreement to be as open-ended as critics contended, he said.
"We believe the Government is well aware of any risks that might arise from the operation of these provisions."
