Former cabinet minister Nick Smith is defending himself over accusations of "money for mates" after an environment consultant friend received hefty fees from the taxpayer.

The former environment minister approved $180,000 in taxpayer money last year to pay for the new Mackenzie Sustainable Futures Trust, set up to help resolve a dispute between farmers and environmentalists over projects in the Mackenzie Basin and Waitaki Valley.

The trust, which initially received $100,000, almost ran out of money in November before releasing its findings.

Its application to the Environment Ministry for a further $200,000 was declined earlier this year, but Dr Smith granted the trust a further $80,000, documents released to Fairfax under the Official Information Act reveal.

Policy think-tank the Ecologic Foundation, which is headed by Dr Smith's friend Guy Salmon, received $88,010 in fees, with Mr Salmon paid $18,000 per meeting for a series of two-day meetings.

Dr Smith issued a statement on Monday afternoon defending the spending, saying it was a "good use of public money".

"The Mackenzie is an iconic area of New Zealand where debate over intensification of agriculture is more contentious than anywhere in the country," he said.

"Millions of dollars were being spent in legal disputes over resource consents, district and regional plan rules, and tenure review. The government wanted to try and facilitate broader agreement on a way forward."

He said the "money for mates" accusation was wrong, because the last Labour government spent far more on Mr Salmon and Ecologic, including a $2.21 million contract on researching alternative environmental dispute resolution through the Ministry of Research, Science, and Technology.

"Labour acknowledged then that Ecologic and Guy Salmon were the recognised experts in these alternative means of resolving environmental disputes," Dr Smith said.

Prime Minister John Key on Sunday said officials will look into the matter.

"I'm sure someone will have a cursory look at it ... Maybe the minister's office or my office ... I don't see it as a terribly big issue but I'll reserve the judgment to go and have a look at it."