That amounted to an international agreement "trying to stop our parliament doing what's right for New Zealanders".
That was wrong and Labour would fight to change that by re-negotiating.
He said three countries, including Australia, had excluded themselves from that aspect of the deal.
Mr Little was asked repeatedly if Labour supported the TPP, but did not give a yes or no answer.
"We are for free trade. We understand the importance for a country like ours for free trade to open access to markets, to help our exporters generate wealth [and] create jobs.
"That's absolutely vital. The TPP does something else and it does something that's pretty rotten actually."
Mr Little said he couldn't say what the party's position on TPP-enabling legislation was until he saw the proposed laws.
He was also asked about working more closely with the Greens, after its outgoing leader Russel Norman suggested a better relationship was needed so the left looked like a government in waiting.
"We are working pretty well together," Mr Little said.
"We did when Russel was leader. [We had] the odd minor hiccup. We're doing it under the new leadership. We meet on a regular basis. We talk."
Labour also kept in close contact with New Zealand First.
On policy, Mr Little said a capital gains tax would not be introduced in a Labour-led government's first term and any suggested introduction would be put to the public to get a mandate.
He also confirmed he would recommend to the conference the party drop its power policy that would set up a single buyer for New Zealand's generation.
He said it was too complex and Labour would need to look at other ways to reduce power prices.