"Mr Ombler is a former deputy State Services Commissioner and is a skilled public service manager with a deep knowledge of the New Zealand public system," Hughes said.
"Mr Ombler has a strong understanding of financial management in the public sector and most recently was acting chief executive at the Canterbury Earthquake Recovery Authority."
Hughes said Ombler was highly regarded, had a reputation for integrity and a thorough understanding of public and financial management.
The appointment is effective immediately and it's expected Ombler will file an interim report on the investigation early in the New Year, Hughes said.
"The allegations of wrongful expenditure have raised serious questions about the conduct and integrity of a former State Services employee."
The State Sector Act grants extensive powers of inquiry to the State Services Commissioner or his delegate.
This includes the legal power to require the production of any records, files or other information, require government employees to answer questions and enter government premises.
The investigation will focus on:
• The circumstances of any alleged unauthorised or unjustified expenditure by Murray of DHB funds;
• Any related or similar conduct by Dr Murray or any related person or third party identified during the course of his inquiry, and;
• Any processes undertaken or decisions made by the DHB relating to any matters he identifies under the first two points.
If appropriate, Ombler will make recommendations relevant to the investigation, including about the conduct of other staff members within the Waikato DHB or the DHB's policies or processes.