A trust responsible for managing the office of the Māori King being investigated by the Charities Service lent $83,000 for travel expenses of a company associated with one of its staff, documents reveal.

The Herald on Sunday also found the Ururangi Trust, funded $1.6 million annually by Tainui, has purchased five new or near-new luxury four-wheel drives over the past two years while at the same time rapidly increasing its borrowing from banks and finance companies.

Ururangi employs nine people full-time, but the bulk of its $860,846 salary bill is split between King Tūheitia Paki and the Trust's executive manager, Rangi Whakaruru.

In Ururangi's annual report for the year to March 31, 2017, published on the Charities Register, the trust discloses it advanced $83,191 for travel expenses of a company called Māori International Limited.

"These transactions were recharged to Māori International [Limited] plus interest at a rate of 4 per cent per annum," the accounts state.

The accounts show this related-party loan - with its unusually low interest rate - was unpaid by balance date with interest increasing the amount due to $84,869.

According to the companies office Māori International Limited is an electricity sales firm and is directed by Whakaruru, Peter Rogers and Ivan Liu Kwan.

Hamilton accountant Rogers, a former president of the Waikato branch of the Institute of Directors, is one of two trustees of Ururangi and serves as its chairman. He did not reply to Herald on Sunday emails or phone calls this week enquiring into the circumstances of the Māori International Limited loan and whether it had since been repaid.

Liu Kwan, a Hawaiian lawyer appointed by King Tūheitia as his ambassador to the United States, declined to answer any questions about the loan or his directorship of Māori International Limited.

"You should probably talk to Rangi Whakaruru, because he has all that information," Kwan said before hanging up.

Whakaruru is listed as being the company's sole shareholder. He also did not reply to emails or phone calls this week.

While the trust was advancing tens of thousands of dollars for the travel costs of a company owned by Whakaruru, it was also buying six-figure automobiles and taking on hundreds of thousands of dollars in debts.

The accounts to March 2017 show $134,652 was spent acquiring a Black 2013 Cadillac Escalade. And financing statements show in the 12 months since the balance date Ururangi has bought a Range Rover, Landcruiser and Corolla wagon - all brand new.

The accounts show the trust, which began the financial year owing only $12,106 in term loans, ended it owing $200,097. Financing statements filed after balance date show additional security has since been pledged to Heartland Bank, Westpac and the Bank of New Zealand.

Financing statements show King Tūheitia and his close adviser Whakaruru have also been busy in the past two years acquiring expensive automobiles.

The King's fleet was bolstered with a 2016 Chevy Silverado, a 2010 Holden HSV, a 2014 Mercedes Benz S350, and a pair of brand-new John Deere earthmovers. Whakaruru, meanwhile, has acquired a pair of new jetskis, and a high-end Ford F150 truck.

Internal Affairs were unwilling to comment on whether the Charities Service were specifically looking into the related-party loan to Māori International Limited or the vehicle fleet.

"We can't comment on this level of detail given the ongoing nature of the investigation apart from repeated that we are making good progress," an Internal Affairs spokesman said.

The Herald on Sunday understands their investigation has involved in-depth interviews with former trustees and is also probing a mysterious $46,000 invoice for a tummy-tuck operation at a private hospital that lacks details normally present that would identify the patient.

Rogers told Maori Television's Kawekorero on Friday night that all was above board. "I think there is always disputes over what is charitable and what is not... but we are absolutely satisfied that all expenditure is charitable," he said.

Rogers "categorically" denied Whakaruru was the recipient of the operation relating to the invoice, but said the King's confidante played a role in approving the payment in question. "Rangi Whakaruru signed it off," he said.

URURANGI TRUST VEHICLES PURCHASED SINCE March 2016

2016 Toyota Landcruiser
2013 Cadillac Escalade
2017 Toyota Landcruiser
2017 Toyota Corolla wagon
2017 Landrover Range Rover