Bristol City Council has voted to become a GM-free zone.
The authority will try to ensure no genetically modified crops are grown on its land following a vote which was unopposed on Tuesday.
The decision supplements the existing policy of barring GM food from services like schools and social service meals.
A council spokesperson told BBC News Online: "We recognise public concern over GM foods and share the view that they are not yet proven to be safe.
"Nor are adequate safeguards in place to protect GM crops from contaminating other crops and wildlife.
"The motion reaffirms the council's position and sends a clear message to government, our suppliers and partners that the city has reservations about GM foods and crops at this time."
The motion will now be incorporated into a report on GM food and crops policy being prepared by council officers for the autumn.
Friends of the Earth is supporting the council's stance.
In February, neighbouring South Gloucestershire became one of the first local authorites in England to become a GM-free zone.