Citing an entitlement to ''free and frank expression'', chief executive Carole Heatly yesterday refused to release the documents under the Official Information Act.
The Otago Daily Times has complained to the Office of the Ombudsman, citing the public interest in plans to cut the board's operating expenditure.
When its 2015-16 deficit projection hit $42million, the board brought in Alma Consulting to review the budget levels of each directorate.
The work was mentioned in a report written by sector leader Chris Fleming about the board's financial plight.
In a letter, Ms Heatly said the board must be able to engage freely with advisers.
''I am of the view that disclosure of draft and preliminary reports of this nature would severely curtail our ability to continue in the future to openly engage with our advisers and for our advisers to openly engage with us.''
The board has hired numerous consulting firms in recent years in a bid to improve its performance, enlisting help from as far afield as the United States.
Spending included $639,000 on PricewaterhouseCoopers for cost-cutting in 2012-13, more than $81,000 on the Advisory Board Company in the United States, and $191,246 on Health Partners Consulting Group for strategic planning.
On its website, Alma Consulting says it works with senior management and boards to increase shareholder value and improve long-term business performance.
