Two marae trustees have admitted stealing large sums of Treaty cash and blowing some of it at casinos – but no-one has told police.

Carlo and Janice Harrison misappropriated at least $20,000 from bank accounts belonging to the Waimapu Marae in Tauranga and, according to a Maori Land Court judge, far more money could have been taken.

The couple have admitted spending the money, meant for marae renovations, at SkyCity Casino in Auckland, Riverside Casino in Hamilton and bars around Tauranga.

There is also evidence of spending at service stations, KFC, Pizza Hut, cafes and department stores.

The bank accounts involved had about $109,000 in them, but most of that is gone.

Trustee Lance Waaka, who blew the whistle on the Harrisons, said there was only about $400 left in the accounts.

The Harrisons, both 63 and sickness beneficiaries, said about $50,000 was spent removing dozens of large trees from the marae grounds and building new fences.

They admitted they had also given money to whanau members who hadn't paid it back.

The judge, Stephen Clark, said in a judgment that as well as 44 Eftpos withdrawals at casinos, pubs and bars which the Harrisons had admitted, there were a number of other withdrawals warranting further investigation.

Describing it as a "pattern of criminal offending", the judge said a proper forensic inquiry was needed to ascertain the true level of the theft, and that inquiry was best carried out by police.

But Waaka said he was unsure if he would lay a complaint, as the Harrisons had already been humiliated. "Some of the whanau want to take it all the way," he said. "It's not right what they done, but say we took it to police, what happens? They just get a bad record and might do PD or whatever."

Carlo Harrison, who described himself as a born-again Christian, said he was prepared to take whatever punishment came to him.

"I said to the judge, I'm prepared ... to go to jail and pay whatever is owed, for the wrong that's been done."

Inspector Clifford Paxton, area commander for Western Bay of Plenty police, said police would wait for any formal complaint before investigating.

The money was from Ngati Ranginui's Treaty settlement, which came in 2012 after almost 20 years of negotiations. The Ngati Ruahine hapu, associated with the Waimapu Marae, received cash and land worth about $2 million.

Judge Clark ordered that the Harrisons, who have 17 grandchildren and 10 great-grandchildren, be removed as trustees and as signatories of the bank accounts, and ordered that they pay back $20,670 to the marae.

He also removed their niece, Erena Ririnui, as a trustee, noting she had failed to act when warned about the irregular expenditure and went on co-signing cheques for her aunt.

The judge said the Treaty claims related to land confiscations in the 19th Century and were hard fought. "It must be galling to right-thinking Ngati Ruahine beneficiaries that so soon after receiving Treaty settlement money ... two persons misappropriated some of it. Their conduct was appalling, they have offered no excuse for their offending."

The Harrisons, who live next to the marae, say they will pay the money back, but have yet to make any payments or organise to do so.

Janice Harrison said her husband had maintained the marae on his own since 2002 with little reward, often paying out of his own pocket.

She said marae money had also been loaned to whanau, some of whom were living in caravans and couldn't pay their power and rent. "We made errors, yeah. A lot of the people here, they get into debt and they come and borrow the money ... and then they don't return it."

They admitted spending the money at casinos, but denied being gamblers.

The judgment reveals a BNZ employee was the first to raise concerns about expenditure from the marae accounts, noticing in March 2013 that more than $5000 had been spent at casinos and pubs. Ririnui was informed at that time.

Waaka became aware of the irregular spending in August, 2014. He organised for one of the accounts to be frozen and sought court injunctions.

Judge Clark was also critical of the Ngati Ruahine Charitable Trust, (NRCT) which transferred the Treaty money to the marae accounts, saying it had failed to monitor expenditure.

He said the trust included immediate family members of the Harrisons, and had initially not wanted the complaint taken any further.

The Harrisons are upset that Waaka went to court, instead of sorting the matter out within the marae committee.

But Judge Clark said Waaka had uncovered a "pattern of criminal offending" and trying to resolve it in-house through mediation would have been inappropriate.

Waaka said he was glad that another $400,000 of Treaty settlement money that was due to have been transferred from the NRCT had not been.