A mother was allowed to leave New Zealand with her son on February 7, 2019, despite a border alert preventing her from doing so.

A police officer who allowed a mother to abduct her young son despite an active border alert had "insufficient knowledge" and understanding of police policy, an investigation has found.

The woman, who has interim name suppression, was allowed to leave from Christchurch Airport on February 7 after the court had ordered the boy be kept in New Zealand.

Stuff earlier revealed the Christchurch Airport-based officer used the wrong computer system to check for information about the border alert and failed to contact Interpol, which was normal practice.

SUPPLIED A mother was allowed to abduct her child and take him overseas because a police officer at Christchurch Airport couldn't find anything in their system, despite a Customs border alert.

The boy's father, who is now suing both Customs and police, first knew of what was happening when the mother sent him a text as the aircraft was departing. The text said she was taking their son to her home country where he would remain until adulthood.

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A summary of the Police Professional Conduct investigation, which also considered whether there was any criminal liability, was released to Stuff under the Official Information Act.

It found there was insufficient evidence to prove the officer intentionally contravened the Family Court order. The incident highlighted a "discontinuity in training" for International Airport Police and an organisational lack of knowledge in the Christchurch Police.

The summary refers to the parents as Ms A and Mr B. Ms A arrived in New Zealand with their child in January and had tickets to return home in February 2019.

On February 1, the Family Court granted an application by Mr B's solicitor preventing the boy's removal from New Zealand and the border alert was issued. Ms A was not at the hearing.

Inquiries later revealed no Family Court documents had been served on Ms A prior to her departure, and there was no evidence she was even aware of the application and the order preventing her from removing the child from the country.

The Family Court said it was not scheduled to advise her until February 13.

On February 5, Ms A went to the Christchurch Central police station and said she was going to leave New Zealand on February 7. During her visit, she was advised by police they were unaware of anything preventing her leaving the country, and was advised to seek legal assistance.

On February 7, the airport police officer made several attempts to contact Mr B's solicitor after Customs Officers provided him with a copy of the border alert.

He then called an off-duty constable who said they knew of no reason why Ms A could not leave with the child. The officer made no further inquiries, despite several options available to him, including the District Command Centre manager, and the on-call Interpol Officer.

The officer's decision was made in "good faith", but was "in direct conflict" with police policy not to allow a child to leave the country without a copy of a discharge order.

Any performance or code of conduct issues identified involving the officer had been dealt with by Professional Conduct and the police's human resources department. As it was an HR matter, no further details were able to be released about the process and outcome.

Police College training has now an updated airport policing training module.

Mr A's legal team declined to comment on Tuesday as the matter was before the courts.