Many China bears, including closely watched short-seller Jim Chanos, have warned that economic numbers from the Chinese government dramatically overestimate growth.
But Robert Barbera, co-director of Johns Hopkins Center for Financial Economics, argued on CNBC on Monday that China's economy is actually contracting.
(Read more: China's 260 million new spenders may save economy)
"If you take the top 10 trading partners with China and you add up their exports to China, you've got data that the Chinese government doesn't get to put their hands on," he said. "If you look at that data, what you've actually got is about minus 4 percent year-over-year."
"China may not even be growing at this point," said Patrick Wolff, founder and managing partner of Grandmaster Capital, a hedge fund launched in 2011 with seed money from billionaire investor Peter Thiel.
The statements are in sharp contrast to China's official assessment of an annual growth rate of 7.5 percent in the second quarter, which marked the ninth slowdown in the past 10 quarters and a dip to the low end of the Chinese government's economic growth target for 2013.
"The current Chinese premier has been quoted in WikiLeaks as saying he doesn't believe the GDP numbers [there]," Wolff said. "People should forget the [Chinese] GDP numbers entirely. They're nonsense."