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Auckland lawyer Paul Cavanagh, QC, says the Electricity Commission's decision to approve Transpower's grid upgrade plan through the Waikato is "flawed" as he prepares to fight the controversial project.

Anti-pylon group New Era Energy (NEE), which represents hundreds of farmers and lifestyle block owners, yesterday announced it would seek a judicial review of how the commission arrived at its July decision.

It has engaged the services of Mr Cavanagh and his legal team, which spokesman Bob McQueen said would cost farmers and landowners up to $1 million.

"It's big bikkies for us. We are going to have to dig deep in our individual pockets and I tell you, it hurts. We have got a reasonable amount of funds in the kitty but we're going to have to pull some more up."

Mr Cavanagh would prepare the request for the judicial review, which would be filed with the High Court before Christmas.

In a statement released through NEE, Mr Cavanagh said he and his client felt they had "a very good prospect for a successful outcome from the High Court challenge on the flawed Electricity Commission decision".

Mr McQueen said a large number of documents obtained under the Official Information Act had been reviewed.

"We are convinced that the commission did not follow the law, they did not follow good processes in making their decisions, and the majority decision they arrived at was not one that a reasonable, unbiased person would make if considering the evidence before them."

Mr McQueen accused Transpower of misleading the public and the Government about the urgency of building the 400kV lines.

The line was "definitely" not needed in the next 20 years "and likely not ever, if upgrading of existing lines and some new generation were to take place soon".

He also said one large 400kV line would reduce Auckland's security of electricity supply by a factor of 18,000.

The Electricity Commission chose not to respond to the announcement yesterday and declined to comment on Mr McQueen's accusations.

It pointed to both an overview of its decision and a detailed paper behind the decision, which were posted on its website.

Both website papers referred to assumptions that had to be made about the timing of the decommissioning of the Huntly Power Station and when a second 220kV alternative line would be required.

While most commissioners made common judgments on these factors, it was acknowledged that commissioner Graeme Pinnell came to a different view.

However, the commission's board was still satisfied it had adopted "reasonable assumptions" and that its conclusion was robust in that it met the "Grid Investment Test".

Meanwhile, Transpower says it stands by its proposal and all figures that were provided to the commission.

Spokeswoman Rebecca Wilson said the grid operator had "not misled anyone at all".

"We've been very open with the process and provided all the information necessary."

If people wanted more information they were welcome to contact Transpower.

"We truly think its the best option for the country, in order to meet the demand in Auckland and Northland," Ms Wilson said.

The grid operator has already bought a number of properties in anticipation of getting over its next major hurdle, obtaining resource consent approval through a Government-appointed board of inquiry.