Environment Minister Nick Smith says there is no conflict of interest in his decision to sack the council of an organisation that is prosecuting his younger brother.

The organisation, Environment Canterbury (ECan), has also rejected any suggestion of bias in its dealings with Dr Smith's brother, businessman Tim Smith - an outspoken critic of ECan.

The minister has moved to have the "dysfunctional" ECan council replaced with Government-appointed commissioners because of what he says is a lack of a plan for water.

He says the failure to come up with a water plan is as "nationally significant" as the failure of transport in Auckland, but critics say the dismissal of the democratically-elected ECan council is an assault on democracy.

Tim Smith, an owner of Smith Crane and Construction, has pleaded guilty to 21 charges brought by ECan for matters largely relating to discharging of wastewater over a Christchurch groundwater protection zone.

He has also faced charges laid by the Christchurch City Council over building consent and fencing issues.

Dr Smith said he was not aware of his brother's "specific issues" until well after he had ordered a review of ECan, which led to the council being sacked.

"I have not allowed my brother's strong views to influence me in my public role."

ECan said its dealings with Mr Smith and his company dated back to 2001. But regulation director Kim Drummond said the organisation had treated Mr Smith the same as any other person it dealt with.

"This investigation and the non-compliances pre-dated the Government review," Mr Drummond said.