Trade Minister Tim Groser has been ordered to take another look at an Official Information Act request in a way which is "consistent with his obligations".

Trade Minister Tim Groser has been ordered to take a fresh look at a request for information on Trans Pacific Partnership (TPPA) negotiations.

Professor Jane Kelsey and others took Groser to the High Court after he refused to release information to her under the Official Information Act. It later emerged that Groser had not reviewed the documents he refused to release, in a blanket refusal for information.

On Tuesday Justice David Collins delivered a judgement in which he said there was was "no lawful basis for the Minister to withhold, in the way he did, some of the information requested by Professor Kelsey".

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Collins added: "It is therefore appropriate for the Minister to ensure officials assess each piece of information requested by Professor Kelsey that is in the possession of the Minister and [Ministry of Foreign Affairs and Trade] MFAT against the criteria in the Act for withholding information".

The decision fell short of a declaration that Groser or officials at MFAT acted illegally in the refusal.

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Groser was however given blunt advice from the High Court, instructing him to review his decision "in a way that is consistent with his obligations under the Official Information Act".

Officials will be required to review "each piece" of information requested.

Justice Collins also sounded a more general warning to the wider Government about the way it handles Official Information Act requests.

"[T]he [Official Information] Act plays a significant role in New Zealand's constitutional and democratic arrangements. It is essential the Act's meaning and purpose is fully honoured by those required to consider the release of official information," Collins wrote.

"[T]he orders I have made reinforce to the Minister and other decision-makers the importance of discharging their responsibilities under the Act and promote future compliance".

During the hearing in the HIgh Court in Wellington on September 28, lawyers for the Crown argued that the request might force officials to look at 30,000 pages of information.

Kelsey said she had been vindicated.

"The Minister's approach epitomises the contempt for democratic processes and accountability that has pervaded these negotiations," she said in a statement.

However she added that Groser's tactic had been successful. Since the Court heard Kelsey's application, the 12 countries involved in the TPPA have announced an agreement, although the final text of the agreement has not yet been published.

"It's cold comfort that the Minister will have to revisit the request, using a proper process and interpretation of the rules, after the negotiations have already concluded," Kelsey said.

"His unlawful approach in circumventing the Official Information Act appears to have achieved its goal."

Groser's office said it needed time to review the decision before commenting.

Greenpeace described the decision as a "humiliating judicial slapdown" while the Green Party said the Government "must change its arrogant approach to the public's right to know about official information" in light of the decision.

However one OIA expert said it may be that Groser's office and MFAT officials had made a basic error in the way it handled the request. Groser could simply have used section 18A of the act, which covers requests involving a substantial amount of collation and research to request further time and possibly inform Kelsey that she would have to pay for the research to be undertaken.

The decision led to a fresh attack of the Ombudsman, which adjudicates on Official Information Act disputes, and upheld Groser's decision not to release information.

The Taxpayers' Union congratulated Kelsey on her court challenge, as it dismissed the Ombudsman's effectiveness.

"This is a significant victory for freedom of information and an embarrassment for the Office of the Ombudsman which has been shown up as lacking. Every day, groups from the Taxpayers' Union to Greenpeace along with public lawyers and political journalists are hampered by a freedom of information system which is being gamed by the government," executive director Jordan Williams said.

"For years the Ombudsman's office has complained that the problems are due to a lack of funding. In reality, the number of appeals relating to the Official Information Act has snowballed because government agencies and politicians know that the Ombudsman is a toothless tiger."

However Chief Ombudsman Dame Beverley Wakem rejected the criticism, saying the decision released by the High Court related only to the process followed by the Minister.

"As the judgment makes clear, the Court was not concerned with the merits of the Minister's decision or the Chief Ombudsman's report following her independent investigation and review. The Court made no finding on whether the Official Information Act provided proper grounds for refusal of Professor Kelsey's request," Wakem said in a statement.

"Any suggestion that the Court passed judgement on the merits of the Chief Ombudsman's decision is incorrect."