"I'm concerned about unintended consequences. I'm worried about how much will be fait accompli." The Public Health Association, Electronic Frontiers Australia, and consumer advocacy group Choice are among many interest groups who have long protested against the secrecy. They claim leaked draft chapters from Wikileaks show the TPP could push up the price of medicines, make it harder to restrict tobacco and alcohol sales, and force internet service providers to aggressively enforce copyright rules. Mr Heffernan said most concerning was the Investor State Dispute Settlement clause, which empowers multinationals to sue governments if new laws such as food safety standards harm their profits. "I want to be asking these detailed questions, about the capacity for corporations to sue governments," he said.

"The average person here in Parliament hasn't got their head around a range of things. If you don't know what's on the table, how do you know what questions to ask?" Mr Robb labelled the complaints as "bizarre", saying Mr Heffernan had been offered briefings and an opportunity to view documents, providing confidentiality was respected. "To the best of my knowledge he has not taken up this offer which is something I am happy to facilitate for any member of parliament," he said. Mr Heffernan said he had not taken up the offer because the TPP was a "directionless, bureaucratic brief", "just a motherhood statement". Instead, he wants to see the TPP released to the public so that it can be tested by people with "dirt under their fingernails". He said: "It ought to pass the paddock test."

Mr Robb insisted many stakeholders were actively participating in ongoing consultations and accused critics, such as the Australian Council of Trade Unions, of pretending to be locked out. "It is naive in the extreme to suggest the government can negotiate such a complex agreement without seeking guidance and advice from various interest groups," he said. "This is precisely how we guard against the unintended consequences that [Heffernan] refers to." There have been a thousand consultations since 2011, including 150 focusing on health-related intellectual property issues. Associate Professor Kimberlee Weatherall, intellectual property expert at Sydney University, has attended consultations and believes they are too general to be meaningful.

She said intellectual property experts like herself were demanding access to the TPP so they can assess the impacts on the public. She said the leaked IP chapter showed the TPP locked in a "20th-Century version of copyright", where copyright owners could control every last copy, including every digital copy and computer memory. "When Bill Heffernan talks about 'unintended consequences' it's because there can be implications that even negotiators aren't aware of. They're not operating at the cutting edge of specific areas, such as quarantine," she said. "They can talk to experts. But it's another thing to have the 'contest of ideas' from different, competing groups so you can thrash out the implications. "We are locking in detailed obligations about how our intellectual property has to look potentially for the next 20 to 30 years. And you can't do that behind closed doors."

Trade officials from Australia, the United States, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam are engaged in closed-door negotiations to finish the TPP in the next few months.