Trade Minister Tim Groser has refused to give details of New Zealand's position in TPPA negotiations.

Officials at the Ministry of Foreign Affairs and Trade (MFAT) may have had to search 30,000 pages of documents to fulfil an Official Information Act request on Trans Pacific Partnership (TPPA) negotiations, Crown lawyers claim.

On Monday a group seeking a declaration that Trade Minister Tim Groser acted unlawfully when he issued a blanket refusal to release information on the TPPA negotiations took their claim to the High Court.

Dr Matthew Palmer QC, representing trade activist Professor Jane Kelsey and seven other applicants, claims the group is simply seeking a standard reading of the Official Information Act and that the group were not "wild eyed radicals" seeking a new interpretation of the law. The hearing is taking place in Wellington before Justice David Collins.

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In January Kelsey sought from Groser a number of document on New Zealand's negotiations in TPPA talks since 2013.

The agreement - a proposed Pacific rim trade pact - has not been completed.

While some draft texts and other documents have been leaked, the negotiations have largely been held in secret.

Lawrence Smith Professor Jane Kelsey, a vocal critic of the Trans Pacific Partnership's negotiation process.

A number of protests have taken place throughout New Zealand demanding that the proposed text of the deal be made public.

Initially Groser's office sought an extension of the time it had to respond to Kelsey's request to allow consultation to be completed, but days later said that it was refusing to release any information.

The High Court challenge to Groser's decision claims the Trade Minister made a judgement about what information the applicants wanted, without even reviewing all of the information request.

While much of the information may have needed to be kept confidential, some of which might have been useful to Kelsey and others without breaching the need for secrecy.

"Blanket refusal is unlawful and should be reconsidered," Palmer said.

Appearing for the Crown, Deputy Solicitor-General Virginia Hardy said that the application by Kelsey and the other applicants were effectively inviting the court to second guess the judgement of both Groser, MFAT officials, and the Office of the Ombudsman, which had upheld Groser's refusal.

The Chief Ombudsman upheld Groser's decision to refuse the request, including on grounds under the Official Information Act which Groser did not cite in his refusal.

This was on the basis that releasing the information was justified to "avoid prejudice to the substantial economic interests of New Zealand".

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Hardy told the court that she had been advised that for officials at MFAT to search through information which may have been covered by Kelsey's request, staff may have had to search through 30,000 documents.

This was in the context of Kelsey requesting the matter be treated with urgency.

"The Minister adopted a sensible approach" and focused on what was central to the request, Hardy said, making the judgement that there was nothing which could be released.

Collins asked Hardy if the minister could have simply written to Kelsey saying it would take months to fulfil the request and they may charge to have the work done, options granted under the provisions of the Official Information Act.

"Nothing would be added by a document by document assessment that that communication may have relayed," Hardy said.

Monday's hearing centres around the secrecy in which TPPA negotiations are being held, but focus of the Court covers the way the Government handles requests for information.

Palmer said that the Official Information Act represented a "sea change" in the way official information was treated when it was passed in 1982, replacing the Official Secrets Act, imposing for the first time a presumption that the information should be released unless there was good reason to withhold it.

"It is not good enough to withhold documents on a blanket basis which the minister assumes are relevant" to the act, Palmer said.

The applicants recognised that there was a need for a certain degree of confidentiality in trade negotiations.

"It is the extent of confidentiality that is being asserted by the Crown that is the problem," Palmer said.

Palmer said that the documents were likely to contain information which the trade minister would likely consider to be anodyne - or run-of-the-mill - like the dates and locations of future meetings, but which others may consider to be important.

The opinion of the trade minister on how important the information is was not a reason for withholding information under the Official Information Act, Palmer said.

"The fact that a minister does not see value in the information cannot be a reason for withholding the information," Palmer said.

"What is anodyne to one person, is valuable to another."

The hearing would not spend much time on the applicant's concerns about the impact of the TPPA, Palmer said, although he raised a particular concern about certification, where the United States could demand another country's domestic law be modified to what the United States saw to be that country's international obligations.

Kelsey's challenge was joined by groups including Consumer NZ, who Palmer said was concerned that the TPPA could have "significant impact on New Zealand consumers".

Other groups involved in the challenge include Oxfam and Greenpeace.