Former Prime Minister Helen Clark says it would be "unthinkable" for New Zealand to be left out of the TPP, as ministerial talks to try to get the deal signed off this week continue in Atlanta.
Ms Clark met with Prime Minister John Key in New York today and spoke to media briefly.
She rarely comments on New Zealand domestic issues, but made an exception when asked about the TPP, which began under the former Labour Government as the P4 with Chile, Singapore and Brunei.
"What always haunts a Prime Minister is 'will there be a series of trade blocs develop that you are not part of?' Because that is unthinkable for New Zealand as an export-oriented, small trading nation.
"So of course New Zealand has to be in on the action with the TPP and go for the very best deal it can as the agreement expands beyond the original four economies to a wider regional agreement."
The Labour Party Ms Clark once led has said it will not support the TPP unless "non-negotiable bottom lines" were met. Those included gains for farmers, protecting Pharmac, ensuring Governments could not be sued for regulating in the public interest and maintaining the right to restrict farm and housing sales to foreigners.
Mr Key said afterwards Ms Clark was right. "She started some of these discussions a very long time ago and we would hope the Labour Party would see that in New Zealand. This isn't about politics - it's about enriching New Zealand." He said modelling had shown it would be more lucrative for New Zealand than the free trade agreement with China, even with a less than satisfactory deal on dairy.
He confirmed Trade Minister Tim Groser had now travelled from New York to Atlanta to attend the negotiations - something Mr Groser previously said he would not do if the parties were still so far apart a deal did not seem possible.
It was still possible the talks would conclude this week. If not, the last possible chance would be the Apec meeting in the Philippines later in the year.
However, Ms Clark's comments angered TPP critic and law academic Jane Kelsey who said it put Ms Clark at odds with Labour's position. "Clark's statement suggests she had become too far removed from the realities and opinions of ordinary New Zealanders." She said the UN's special rapporteurs had voiced concern about the TPP's impacts on human rights.
Mr Key said many of Ms Kelsey's arguments against it would evaporate once the details were revealed.
Earlier in the day Mr Key had addressed the Asia Society in New York. He was unapologetic when Japanese media said New Zealand had been criticised for the level of access it wanted. Mr Key replied that New Zealand and the three other founding countries for the TPP had agreed it must a comprehensive trade agreement. That was made clear to latecomers including Japan and the United States as a condition of them joining.