A Northland high school teacher who spent nearly $100,000 clearing his name against indecent assault charges says police bungled the investigation.

The man, who cannot be named due to court suppressions, said he was not angry at the four girls, whose accusations nearly ended his 25-year teaching career.

"I've lived my life long enough to know some people do have malice in them, but my feeling of this is more it was a total botch up of a kid who had some mental health needs."

The teacher was acquitted following a criminal trial and has now lodged a formal complaint with the Independent Police Conduct Authority (IPCA).

His comments follow those of another Kiwi teacher who was cleared last week of indecent assault allegations and who said he felt let down by the system during his "year of hell".

The Northland man was found not guilty of six counts of indecent assault by a jury in March last year according to a letter from the man's lawyer, sighted by the Herald.

The same letter showed the man spent more than $90,000 on legal fees to clear his name.

The girls were 14 at the time they claimed their teacher groped them during class.

Three girls said he touched them on their bottom and one said he touched her breasts.

Following the allegations, which came out over the course of a year, the man was arrested in September 2015 and granted name suppression at his first court appearance.

The man told the Herald that, despite the suppression order, a police officer named him at a public meeting and declared him guilty to an assembled group of parents and students.

He said the officer told the group that "I was a guilty man, I would be found guilty, I would go to jail."

Students were interviewed by the same officer the next day and some gave evidence which the man said twisted innocent comments he had made during class.

He believes the students were trying to be helpful and had their impression of him tainted by the officer's words.

The man said his faith in the police was now virtually non-existent.

He has filed a formal complaint with the IPCA.

The IPCA did not respond to request for comment by deadline.

In a statement, a police spokeswoman said police could not comment while the matter was being investigated by the IPCA but were "co-operating fully with the IPCA".

The man said no one could comprehend how devastating something like this was until they experienced it.

"It's like mourning your job. You're mourning your dignity," he said.

"There's nothing worse you can be accused of than something sexual against a minor.

"It's a disgusting thing to be accused of."

The teacher was suspended from his job on full pay. After an internal investigation by the school's board of trustees following his acquittal, he'd returned to working at the school.

He said he was grateful for the school's support, though he wished the internal investigation had not taken so long.

To be teaching again was a relief — at one point he thought he could never return to the job for which he feels an enormous passion.

The man's kaupapa as a teacher was about helping students, he said.

The man said the teenage girls' accusations lacked credibility. The first two complainants said they were certain no one had seen him touch them inappropriately, despite the alleged incidents occurring in the middle of a full classroom.

The man said he had touched one of the girl's waist to get her to move aside on one occasion, after asking repeatedly for her to move and being ignored.

He admitted this from the beginning, and said he wished he'd had the chance to talk to the girls through a mediator at the school before the situation escalated "so they could have seen quite clearly that I didn't mean anything bad [by that]".

"I think they painted a worse and worse picture of me in their mind as time went on."

One of the girls was troubled, he said, and he believed she may have swayed others into making allegations against him.

However he was not angry at her, rather the police who he felt were too credulous about her allegations.

The man said he was working through post traumatic stress disorder symptoms.

"I understand they're trying to find a balance and in the past it was highly likely there wasn't a balance and people weren't being prosecuted when it turned out they were guilty.

"I fully understand why they're on edge and they really want to get offenders. But … you're innocent until proven guilty."

The school's board of trustees referred the Herald to a lawyer for comment, who did not respond to requests by deadline.