Mr Lees-Galloway said the commission, whose functions were this month merged with that of the Health and Disability Commissioner, was "gutted" of staff too early.
This led to "ridiculous" outsourcing to the private sector to develop an important document - Blueprint 2 - which sets out a 10-year plan for mental health.
It is not binding, but will be taken into consideration by the Ministry of Health, which is developing a three-to-five-year policy for mental health and addiction.
Core roles like developing sector plans should remain in-house, Mr Lees-Galloway said.
Figures released to the Otago Daily Times show private consulting firm Synergia received $346,800 in 2011-12 to lead development of Blueprint 2, including providing a dedicated writer.
Synergia also received $95,000 in 2010-11 to lead development of a "sustainable investment pathway for mental health and addiction".
That year, the company received a further $84,000 from the commission to prepare a statement of intent, a statement of forecast service performance, a work programme for 2011-12, a briefing paper for the State Services Commission, a literature review, and editing reports.
It is unclear whether the figures include GST.
The ODT has requested the full cost of developing Blueprint 2, which is being considered by the Ministry of Health.
Asked about the outsourcing, Health Minister Tony Ryall and Associate Health Minister Peter Dunne referred the ODT to officials.
Through a spokeswoman, Mental Health Commissioner Dr Lynne Lane said the commission's board was "fully satisfied" with Synergia's work.
"It was a large project and completed on time with a high level of support from senior stakeholders."
Asked if more such outsourcing was likely, given the commission no longer existed, Dr Lane said work would only be outsourced if required skills and expertise were not internally available.
The Health and Disability Commissioner planned to recruit expert staff for its new mental health responsibilities, once a work programme had been determined, Dr Lane said.
The Ministry of Health would consider Blueprint 2 as it developed a mental health and addiction policy, due for release later this year, Dr Lane said.
Budget documents released late last month show disestablishing the Mental Health Commission saved just over $1.1 million in 2012-13.
The same paper reveals the Government is targeting 10% savings in mental health over four years.
Mental Health Foundation chief executive Judi Clements, who was an adviser for Blueprint 2, said the document was significant, and required a lot of work.
She said Synergia was only one of a number of private contractors helping public servants develop the document. Many of the private consultants were former public servants, she said.
An update to the 1998 original, Blueprint 2 was released last month, recommending flexibility to allow funding to shift from specialist services to benefit a wider group.