"Millions already wasted $80mill [sic] more at stake @auditor-general STOP. THIS. NOW! HBRIC wants $500k to start dam work," Mr Frame tweeted.
In answering his tweet, the Auditor-General apologised for the delay in her reply. "We received a request to look into this; we'll let you know if we have any public updates," she said.
When asked about a potential investigation, a spokesman confirmed the office had received requests to inquire into matters relating to the Ruataniwha scheme. "We are in the process of deciding whether to investigate," he said.
"Generally, when we receive an inquiry we do some preliminary work, such as reviewing evidence provided to us and talking to the entity, before deciding whether a more significant inquiry needs to be carried out.
"To be clear, none of the entities you referred to [the council and its investment arm] are under investigation."
When asked about the possible investigation, the council's chief executive Liz Lambert said it was the first time she had heard about it and so she really could not comment on the matter.
Regional council chairman Fenton Wilson clarified the original matter that the investment company statement of intent, which was approved by the full council, allows the company to borrow against their balance sheet.
"The council were advised, as a matter of courtesy, by HBRIC at an open council meeting they needed to increase the borrowing provision which we voted in favour of," he said.
When speaking about the request for the money last month, company board chairman Andy Pearce said the reason for the shortfall from the ministry was because it said money for early geotectonical work was not required to reach financial close, one of the conditions precedent that had to be met before the project could go ahead.
Councillor Peter Beaven said at the time that the council should not be spending a single penny more than was required to meet the four conditions precedent.