The Flood & Water Management Act, which was given Royal Assent on 8 April, will allow the Environment Agency to flood any areas it sees fit - including fertile growing land (Grower, 19 February) because flood barriers are expensive to maintain.
The NFU said it feared that the act failed to consider the scale and impact of proposals on the ability to produce sustainable food.
More than half of grade one agricultural land lies within five metres above sea level and 40 per cent of vegetables produced in England and Wales are produced in low-lying fens.
Small farms with on-site reservoirs could also be affected by reclassification, with thresholds of large reservoirs being reduced from a current capacity of 25,000cu m to 10,000cu m.
NFU water policy adviser Jenny Bashford said: "We will continue to press for food policy to be a material consideration in the flood risk management process."