The Green Party says Agriculture Minister David Carter has an undeclared conflict of interest over water management issues in Canterbury.

The Greens, who opposed the Government's move this week to strip elected Environment Canterbury (ECan) officers of their roles in favour of commissioners appointed by itself, pointed out in the House yesterday that Mr Carter owns a farm in the Hurunui district, which falls under ECan management.

A bill giving effect to the Government's plan was introduced under urgency this week by Environment Minister Nick Smith and passed.

Greens co-leader Russel Norman said the bill would ease the consent process and construction of a proposed irrigation dam on the Hurunui River.

"Minister Carter owns a farm in the area that would benefit financially if it did," he said. Dr Norman said the potential conflict of interest should have been declared by Mr Carter when the bill was discussed by Cabinet.

But in response to a question from Dr Norman, Prime Minister John Key said he could not recall any conflicts of interest being declared.

Dr Norman also alleged Mr Carter made an "inappropriate approach" to Forest & Bird South Island conservation manager Chris Todd last year, asking him and others to "freeze" proceedings to oppose the Hurunui dam for 12 to 18 months while a negotiated settlement was pursued.

Mr Carter said Dr Norman's claims were "scurrilous".

He had consent to irrigate his property from the Hurunui River, which would not be altered should the dam go ahead and therefore did not stand to benefit.

He said he discussed the Hurunui scheme "with all parties involved" last year in a bid to avoid "combative and expensive" Environment Court proceedings.

"I am surprised that the Green Party is not more supportive of this consensus-building approach."

Dr Norman, with Labour MPs, has attacked the Government's ECan plan as undemocratic.

Dame Margaret Bazley will head the team of commissioners, and up to six more are yet to be appointed to run ECan until local government elections in 2013.