Opponents of genetic engineering believe Auckland Council's decision to become officially GE-free will be good for business.

Auckland councillors have agreed to ban the general release of genetically modified organisms under the Unitary Plan, a 30-year combined regional and district plan.

The decision comes a year after Hastings District Council agreed to ban the outdoor use of genetically modified organisms in its district plan.

Soil and Health Association chairwoman Marion Thomson said all councils should be taking a long-term precautionary approach to any untested GM technologies.

"We've just submitted into the Marlborough district plan. We are about to launch into every council that has a review coming up."

Ms Thompson said Auckland's GE-free status will be good for its local and international reputation.

"New Zealand's got a real potential for a marketing edge. GM technologies are really not yet proven."

The decision of both Auckland and Hastings to become GE-free has sparked calls for other districts to follow suit.