Cabinet will agree the terms, sign the agreement and ratify it. It will then be down to Parliament to enact any legislation needed to bring the terms into effect and make them New Zealand law.
Mr McDouall said Labour wanted the text of the agreement released.
"We are not against free trade but we want the text made public," he said.
"There is a lot of disquiet about New Zealand losing sovereignty around intellectual property rights and Pharmac, the national drug-buying agency. "If we knew what we were debating, there could be a lot of public clamour."
Rally organiser Raewyn Roberts told the Chronicle she understood Mr Borrows to say the agreement would be put in front of Parliament before being signed.
But yesterday Mr Borrows said: "This is the way we've always done free trade agreements. The proposal is agreed between parties and then goes to Parliament to be passed into law.
"If you don't pass it into law, you are not part of the agreement - it won't exist unless Parliament votes for it."
However, Mr McDouall commented: "It is endorsed by Cabinet and that locks in New Zealand's position - we can't change it.
"Cabinet is the top of the tree. I feel they are a Cabinet of corporatists who will accept and ratify it and not expose themselves to democratic scrutiny before signing."
One of his concerns over the TPPA was that foreign corporations could sue a government if it took action which reduced their profits.
He said "an incredible cross-section of people" were opposed to the secrecy over the deal and it was "an election issue, for sure".
Auckland University law professor Jane Kelsey has raised problems with the TPPA.
"First, much of this will not require legislation - it could be done by regulation, administrative decision, policy directives, or simply locks in a problematic status quo," she said.
"Second, the amendments are likely to be in an omnibus bill that would go to the foreign affairs, defence and trade select committee and be subject to the truncated timeframe."
