Cameron said people were increasingly interested in what they ate, how it was grown and the effect on the environment.
“Politicians should ask what more we can do to expand farmers' markets, increase branding of top-class UK produce and increase transparency, so consumers know exactly what they' re buying and eating,” he said.
“That's the way to support our agriculture, to foster good practice, to sustain the environment and to give people the high quality food they want.”
Patrick Holden, director of the Soil Association, said millions of people from all social and income groups were buying organic food and an increasing number were asking that it be locally grown and seasonal food as well.
The 60th Anniversary Conference, Feeding our cities in the 21st Century, includes speeches from Mayor of London Ken Livingston, director general of the BRC Kevin Hawkins and Jonathon Porritt, Chair of the Sustainable Development Commission.