China's top grain trader, Cofco Ltd., has criticized the U.S. Department of Agriculture over a recent report on corn acreage that sent prices plummeting last week.

On June 30, the USDA forecast that 92.3 million acres will be planted this year in the U.S., a significant rise from a report only three weeks earlier, which forecast 90.7 million acres.

"The USDA corn data is an insult to corn researchers like us," Fei Zhonghai, the chief risk manager at state-controlled Cofco, said at a derivatives forum in Dalian Wednesday, according to a transcript posted on the Dalian Commodity Exchange website.

"I don't know if it is that U.S. researchers lack ability or if the USDA has only limited surveillance capacity. If it is [either of these], I think they shouldn't routinely release their data, because the harm they cause to investors is too great."

"If this is the standard of their data, companies are unable to hedge on the futures market, and it can bring huge losses to our enterprises," he said.

-Zhoudong Shangguan contributed to this article