Chinese commercial banks' bad loan is so vast and rising so fast that more capital might have to be injected into banks to buffer the shock, said Xiang Songzuo, chief economist of Agricultural Bank of China, in the 2015 Finance Elite Summit held Thursday in Beijing.

"There's a huge question mark on whether the current capital of banks could withstand the rapidly rising bad loans," said Xiang.

According to Chinese Banking Regulatory Commission, non-performing loans in commercial banks by the end of June has grown to 1.8 trillion yuan ($285 billion), or 1.82 percent of the total asset.

Xiang expects the non-performing loans to reach two percent by the end of this year, and for some individual banks, the ratio to climb to three percent.

"Even that is an underestimation. When I was informed the actual NPL ratio in some banks' local branches, even I, as a veteran banker, was taken aback. The question is who would pay for the capital injection. How would shareholders of those banks willing to pay for the bill?" said Xiang.

The hike in bad loans is the result of the relentless credit expansion after 2009 to maintain a GDP growth rate.

"China should reflect its past "paranoid" with the "GDP growth speed" and completely abandon the deep-entrenched obsession with single GDP number. The belief that credit expansion is omnipotent has bankrupted. People should stop talking about whether the GDP should grow at 7 percent, 6 percent or 5 percent."

Xiang cited a research by the central bank illustrating the sharp decline of China's credit effect. From 2003 to 2007, every one percentage point of credit growth could yield an additional 0.73 percent points of GDP growth. During 2008 to 2013, the yield fell to 0.47 points.