Foreign Minister Murray McCully said yesterday that on June 9 he signed a document that waived immunity for the diplomat, which allowed local police to interview the man.
"I think it is well established that we expect diplomats in New Zealand to behave well and be accountable under our laws, and we try and take the same approach in other people's jurisdictions."
Mr McCully would not go into the details of the allegations, or give details about the seniority of the diplomat, but said it was not New Zealand's ambassador.
The person was connected to the embassy.
A spokesman for the Ministry of Foreign Affairs and Trade said a waiver was very rare.
"Apart from this case, there has only been one other incident in the last 10 years where a waiver was granted to allow a New Zealander to be interviewed by police. In that case no charges were laid or convictions entered.
"However New Zealand regularly waives diplomatic immunity for its staff and their family members serving offshore for a variety of routine reasons, for example waivers in order to allow entry into property leases."
This year Malaysian diplomat Muhammad Rizalman bin Ismail was sentenced to nine months' home detention after he broke into the home of a Wellington woman without his pants and defecated outside her home.
The envoy left New Zealand in 2014 despite facing attempted rape charges after a botched email gave Malaysian officials the impression he was entitled to diplomatic protection and it would be acceptable for Mr Rizalman to return to Malaysia.
He was returned under extradition on October last year and pleaded guilty to indecent assault in November. He was sentenced in February this year.
More than 60 diplomatic staff or family members have sought immunity for offences committed in New Zealand in the past 20 years, including for 25 serious criminal matters of a sexual or violent nature.
New Zealand officials applied to have diplomatic immunity waived in 13 of these cases, which range from drink-driving to assault, and a waiver was granted on seven occasions.