The Cabinet Office Food Matters study warned that it was unclear whether local food was more environmentally friendly and that food miles were a "poor indicator" of environmental impact.
A whopping 26% of UK agriculture's energy was used to grow fruit and vegetables in heated greenhouses, the report claimed, and growing tomatoes in the UK used 10 times as much energy and emitted four times as much carbon dioxide as producing and importing tomatoes from Spain.
Asda said that both local and imported produce had a role to play.
"We take a common sense approach to retailing to ensure that seasonality is a key driver," said a spokesman. "Where it makes sense for the customer and the environment, we will source locally. When items are sourced abroad it is because it provides better value to the customer and a smaller carbon footprint."
Meanwhile, the Association of Convenience Stores said retailers needed more support on the environmental impact of produce.
"We want to help educate retailers about the issues, and explain the decisions that are involved in green and local retailing," said Shane Brennan, public affairs director at ACS. "But to do this we need the government to provide leadership on what is best."