The TPP has been negotiated since March 2010 and includes countries representing about 40 per cent of world GDP.
The deal includes intellectual property rights, foreign investment rules, labour and environment standards, procurement policies, state-owned enterprises and competition, and disputes procedures.
Labour announced its position last week, saying it would support the TPP only if several conditions were met, including allowing a ban on foreign purchases of residential property and the protection of Pharmac.
It said that if such conditions were not met the deal would undermine New Zealand's sovereignty.
The Green Party has been stronger in its criticism, saying it is totally opposed as leaked draft texts showed the TPP would contain provisions that could hinder access to affordable medicines, stifle high-tech innovation and limit the ability of future governments to legislate for public health and the environment.
Today, Mr Key said he understood the China Free Trade Agreement, signed by Labour in 2008, had been 11 times more successful than the most optimistic economic modelling, and he took a pot shot at Labour for now not supporting a deal with the United States and others.
"[Does] Phil Goff, who seems to have dedicated his career to trade and opening up trade, along with Clayton Cosgrove and others, really believe it is in New Zealand's interests not to sign a free trade agreement with the biggest economy in the world and the fourth biggest economy in the world? It is just barking madness.
"Actually they do, it's just Andrew Little is desperate to try and find a way to keep the left flank of his caucus in check."
However, Mr Little has said the party's TPP policy "had been the subject of discussion by caucus" and the final position had been agreed to by all members.
"We're a party that supports free trade. We have considerable concerns about the TPP ... what I don't support is an agreement that goes beyond just market access and has the potential to interfere with our national sovereignty."
