Senior doctors are calling for an independent health impact assessment of the Comprehensive and Progressive Trans-Pacific Partnership agreement.

They are concerned over the long-term impact the Comprehensive and Progressive Trans-Pacific Partnership agreement could have on the government drug-buying agency PHARMAC.

Despite the US withdrawing, 11 countries including New Zealand, have agreed to go ahead with the deal after Canada which had some reservations came to the party.

Acting executive director of the Association of Salaried Medical Specialists Angela Belich said there is a risk the deal could set health legislation in stone.

"We need someone to look at the agreement from an independent point of view, somebody with some expertise to flesh out what the impacts may be over time of this agreement."

Belich said they have strong concerns about the likely impact of the trade deal.

"The government keeps on assuring us that there are no threats to PHARMAC, it's clear that some progress has been made on that but we need that fleshed out more and we need somebody independent to look at it. We are also concerned about the climate change impact."