Waitangi National Trust, the organisation that administers the Waitangi Treaty Grounds, says an inquiry is under way into financial irregularities in its accounts.

Dennis McBrearty, acting chairman of the Waitangi National Trust Board, confirmed that an investigation was conducted as soon as the irregularity was discovered by the organisation.

That had now been passed to the Serious Fraud Office to make its own inquiries.

"The matter is now with the SFO and we will await the findings of their official inquiry. We are unable to comment any further pending the outcome of the SFO inquiry."

McBrearty said he believed the "irregularities" were relatively recent and had only become apparent in the last month. It is thought the transactions were in a 12-month period starting in 2016. The problem was picked up during routine analysis.

The sum involved in this case is believed to be at the lower end of what SFO investigates, but the Office became involved because of the high-profile nature of the organisation.

There had been no indication how long the SFO inquiry might take, McBrearty said.

The SFO would only say it had picked up the matter.

"We will not be making any further comment at this time."

In the year to June 2016, the trust earnt $11.5m in revenue and had $28.5m in net assets.