Te Urewera trial cost is $3.6 million and rising

The investigation and prosecution of the four defendants in Te Urewera trial has cost the Government $3.6 million.

Documents released to Radio New Zealand under the Official Information Act, show legal aid fees for the four defendants are $1.06 million with invoices still to be processed.

Legal aid fees for the 14 people who had charges against them dropped last year is $1.7 million.

Crown solicitor fees for the prosecution case are $322,412.

While the police operation and investigation cost $500,462.

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Investigation warranted - former police minister

The police minister at the time the Te Urewera raids were carried out is backing calls for an investigation into how and why they took place.

There are calls to look into all aspects of the case, once the four people convicted Tuesday have been sentenced in May.

Labour MP Annette King says she had no input into the raids and was only advised by police the night before they were carried out.

Ms King says people deserve a thorough investigation, saying she feels for people who were caught up in the raids, particularly children.

But she would not comment on whether they should be compensated.

Prime Minister John Key, however, says there is no need for an inquiry into how police and the Crown handled the Te Urewera raids case.

Mr Key says it has been a fraught and complex case.

Green and Maori parties criticise wasted money

The Green and Maori parties have criticised the amount of money spent in bringing to trial four people in connection with police raids in Te Urewera National Park in 2007.

Tame Iti, Te Rangikaiwhiria Kemara, Urs Signer and Emily Bailey were found guilty of firearms charges, however the Auckland High Court jury failed to reach a verdict on whether they were part of an organised criminal group.

The Green Party's Corrections spokesperson, David Clendon, says it is an embarrassment that the large operation has secured just a few low-level firearms convictions.

"I think we need to investigate how this happened, why such poor judgements were made by the police and by the government of the time."

Te Ururoa Flavell, the Maori Party MP for Waiariki, says a lot of money has been wasted, despite the Crown's case diminishing as charges against 13 other accused were dropped.

But the officer who led the operation, Detective Inspector Bruce Good, says the cost was worth it.

"Well, at the end of the day it's cost a significant amount of money for resources ... but we've stopped some activity that was greatly concerning to me."

Listen to more on Morning Report ( 2 min 40 sec )

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