South Gloucestershire has become the first major local authority in the country to become a GM-free zone.
Some environmentalists have protested against GM crops
The motion was approved by the majority of the local council after seven hours of discussion on Wednesday.
The aim was to protect the health of local people and the environment, and to support and promote a viable food economy, say the council.
The local Friends of the Earth spokesman, Tony Harding, said he was delighted by the outcome.
He said: "I am firstly amazed at the stamina and perseverance of councillors.
"I was worn out simply observing the meeting - heaven knows what it must have been like taking part."
The council motion recognises
that genetic modification of plant crops is an evolving science
that there is continuing public and scientific debate and disquiet about the desirability and the safety of genetically modified food
that having accommodated one field trial that caused more concerns than it resolved, the council declares that South Gloucestershire shall become a GM-free zone with immediate effect.