Mr Parker, who was in the region to meet with Pure Hawke's Bay, said if the proposal was passed it would affect Hastings District Council's bid to be GMO free.
"For the first time ever if this passes 360D will enable the Minister to override rules in district plans," he said.
He said this would mean that if a district plan had a rule that prevented the use of GMO in food production it would be overruled by ministerial edict out of Wellington.
"This provision in the RMA would introduce a new principle into New Zealand's law where Wellington could override Hastings, which is just wrong. It is an atrocious grab for power.
"We oppose it - there is no need for that clause."
Hastings District Mayor Lawrence Yule said while he understood it was the Government's responsibility to set national legislation and rules - this clause came as a surprise.
"Effectively if this provision, and how it would be used is yet unknown, but if it was rolled out and there was the ability to unravel a local rule then as a local mayor I say, 'How fair is that?'"
He said one could argue whether it was a way of "stymieing" the council from making decisions, such as the Hastings council's want for the district to be GMO free.
"Another risk in this is that somehow the Government changes the law because we are operating under the current law so if the Government wants to change the RMA then we want to make sure that our decision making is not stifled by it," he said.