Labour leader David Cunliffe intervened in a meeting of affiliated unions at the party conference in Wigram to broker a compromise resolution on the Trans Pacific Partnership.
The Engineering Printing and Manufacturing Union had moved a motion wanting the party to oppose the TPP, in line with a position taken by the Council of Trade Unions conference last month.
The would have posed a major shift in the party's position.
Mr Cunliffe attended the affiliated union council with deputy leader David Parker and the leading TPP sceptic in the caucus, Grant Robertson.
In the end Mr Cunliffe got a consensus to support a Dairy Workers' Union resolution to ''withholds support for the TPP until full details are made available and there is clear evidence that the agreement is in the best interests of New Zealand."
The motion said that the party currently withholds support on the ground that first, the Government has not been adequately transparent in the process and secondly, that the Government is undertaking unacceptable risks on a range of matters, including the ability of companies to sue the Government and the role of Pharmac."
Trade spokesman and former Trade Minister Phil Goff said that stepping back from outright opposition 'Was a very smart move on the part of the affiliates."
"I think it is a recognition of the reality that there are things in a TPP negotiation that will work work in favour of New Zealand."
The Dairy Workers, for example, would want the 200 per cent to 300 per cent tariffs on dairy products imposed by Canada to be removed, and likewise in Japan.
"What people are worried about is whether the Government will go in a new direction in terms of restricting a properly elected Government in New Zealand to regulate for the public good."
When a Labour Government negotiated the China and Asean free trade agreement, it preserved the right of a Government to regulate in areas such as health including tobacco and gambling and degradation of the environment.
"That's critical to how delegates feel about this."
EPMU affiliates delegate Paul Tolich told the Herald his union had put up the motion to oppose the TPP "taking a lead from the CTU conference."
"We are concerned very much that we are moving past free trade in tradeable goods, which the union supports."
The union was also concerned about the TPP giving multinationals and other Governments the right to challenge New Zealand state's right to pass its own regulation as a sovereign nation.
"The affiliates were able to have a good discussion with the Labour leadership and we came to agreement on words that we were all satisfied with."
The policy position is expected to be endorsed by the Labour Party conference tomorrow.