Criminal charges will not be laid against two police officers who misled a court about an illegal raid described by a judge as "consciously reckless".

But an internal investigation into Senior Sergeant Rod Carpinter and Constable John Grantham is continuing, more than a year after the judge's severe criticism.

Justice Christopher Allan found the officers' failure to disclose important evidence had "materially misled" the court and defence, he wrote in an August 2011 judgment.

As a result, evidence in a bust led by Mr Carpinter was dismissed and two men caught with more than $1 million of class-A drugs escaped charges.

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Armed Morrinsville police caught the men, who have name suppression, with 1.6kg of methamphetamine and manufacturing equipment in 2009.

Mr Carpinter is the Matamata-Piako region's sub-area manager, having been promoted less than two months before Justice Allan's criticisms sparked an investigation.

He has remained in the role while under investigation, and his tasks have included overseeing Police Conduct Authority inquiries.

Yesterday, Waikato district commander Superintendent Win van der Velde said police were restricted in what they could say as the matter was under investigation.

"This matter has been the subject of an extensive criminal investigation which failed to establish any criminal liability," he said. "It has since been advanced through independent legal advice and is now the subject of a police internal employment investigation."

Mr van der Velde said it was important for such investigations to follow due process and not be hampered by time pressures.

Justice Allan's judgment on the police raid overturned his earlier ruling that although the raid was illegal and "muddled and sloppy", the seriousness of offending meant the evidence could stand.

His change of position came after the defence presented further information that directly contradicted police evidence and showed the force had not given the defence vital details on database searches.

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"The court is obliged to accord very significant weight to the maintenance of a justice system that is above reproach," Justice Allan said.

"I consider both the defence and the court have been materially misled by a failure to disclose important evidential material.

"The police were consciously reckless ... My concern is heightened by the tendency of some of the police evidence to paint an incomplete picture."