Ms McCarthy says the coalition is putting the future of allotments at risk by threatening to abolish legal protection for local growers.
The Government is considering ditching the law that requires councils to provide allotments where there is a local demand.
The duty to provide allotments has existed for more than 100 years and is set out in the Small Holdings and Allotments Act of 1908.
Ms McCarthy said: “The Government needs to seriously rethink this environmentally damaging proposal.
“Allotments are extremely popular in Bristol as many people want to reduce their carbon footprint and save money by growing their own food.
“The Government is in danger of not only ripping up important protections for allotments that have existed for over 100 years, but also destroying vital green areas where the local community can take pride in growing its own food.”