More teachers who worked with convicted sex offender James Parker have contacted police about his "concerning behaviour" since details of his lurid past were made public last week.

And the Weekend Herald has learned the Ministry of Education did not know about an earlier police investigation into Parker, and was not monitoring him.

Parker had been teaching since about 1996 and was the deputy principal at Pamapuria School in Kaitaia when he was arrested and charged with 49 counts of sexually abusing young pupils.

He admitted all of those charges in the Kaitaia District Court last week. It has since been revealed that police investigated Parker in 2009 after complaints were made about his behaviour towards pupils. No charges were laid as police could not substantiate the claims.

However they wrote a "strongly worded" letter to the school about Parker.

His first principal then spoke out about raising concerns with police in 1996 when Parker was a first-year teacher.

She complained to an officer in Kaitaia about Parker hosting pupils in his home overnight and sharing his bed with them.

She said her complaint was never dealt with properly.

A former pupil of Parker's told the Weekend Herald that the board of trustees at his first school was also aware of the principal's complaint to police and her concerns. However they supported Parker and did not support the principal's claims, the former pupil claimed.

The Ministry of Education said this week that it did not receive any complaints about Parker in the 1990s. And they had not been monitoring him in anyway in spite of the 2009 allegations.

"The ministry did not become aware of any concerns regarding him until his arrest this year," said spokeswoman Emma Peel.

The ministry was not carrying out its own investigation into Parker.

Police said earlier this week they had received about 30 calls relating to Parker, from various parts of New Zealand. It was too early to say whether those calls would lead to fresh charges.

Their investigation is continuing and they have repeatedly appealed for any other victims to come forward. This week they refused to say what new complaints had been made.

But they said that until the "current" charges were laid they had "no record of complaint or disclosures of abuse" from the principal or pupils at the school where Parker worked in 1996.

"As a result of the current charges police have received information from teachers referring to concerning behaviour during his teaching years including from the mid-1990s," said Northland police spokeswoman Sarah Kennett.

"Those reports, including whether police were notified at the time, now form part of the continuing investigation and as such will not be commented on any further."

Police refused to comment on the officer who reportedly took the 1996 complaint, or say whether he was under investigation.

Parker's family were not ready to speak about the charges.