“Neither the foundation nor the government has any evidence to back up the claim that it has a terrific capacity to leverage private donations from public money,” Senator Keneally told Fairfax Media.

A foundation spokesman said the question of the group's total fundraising had been raised at the inquiry and an answer would be provided “to the Committee as requested”.

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“The foundation is the best-placed organisation to leverage further investment from the private sector,” he said.

“We have an 18-year history of cultivating the partnerships and projects that draw out the best science, technology, research and conservation ideas to protect and restore the reef.”

Mr Frydenberg defended the funding, saying it would “protect the reef and drive further philanthropic and corporate support”.

“The Great Barrier Reef Foundation is a highly respected philanthropic organisation” with “a long track record of working with government, private sector and the university and the CSIRO”.

Prime Minister Malcolm Turnbull and Mr Frydenberg met foundation chair John Schubert on April 9 without any department officials present.

The Senate inquiry is seeking to interview Mr Turnbull to determine what advice the PM sought or received about the meeting. That includes what financial risks were associated with granting a sum to the group that was 105 times larger than any previous single-year grant, Senator Keneally said, citing the analysis.

Labor claims the foundation spent only about 57¢ in each dollar raised on scientific research.

The foundation spokesman said that in relation to the Reef Trust Partnership part of its operations “in recent years, we have maintained administrative costs under 20 per cent”.

Labor also queried the group's spending on employees, noting it clocked up $1.3 million in staff costs each year for the past two years for its tally of six full-time employees and five part-time employees.

The foundation's spokesman confirmed those numbers were correct. Anna Marsden, its managing director has an annual salary is $190,000, he said in answer to a question from Fairfax Media.

During the inquiy's hearing on July 30, Deb Callister, an assistant secretary in the Department of Environment and Energy, said the department had not examined all of the foundation's annual reports at the time of the grant's determination.

“As part of the process that I was talking about before where they had to provide a response to us on the grant guidelines, they did give us quite a lot more information, including copies of audited reports,” Ms Callister told the inquiry. “I don't think it would have gone back to 2011.”