World Trade Organization rules are "inadequate" in protecting interests of developing countries and the organization has "encountered massive difficulties" in carrying out its core functions, said a former People's Bank of China governor.

In a sharp critique of the international trade body, Zhou Xiaochuan essentially called it toothless and ineffective.

"Today, WTO rules fall short of addressing challenges of the 21st century concerning economic globalization," the former governor at China's central bank said at the Singapore Summit on Saturday.

"They have also been inadequate in terms of protecting the interests of developing countries, especially those that are relatively impoverished," Zhou said, adding that the WTO "cannot effectively discipline" activities such as services trade and investments.

Further, he said, the WTO has "encountered massive difficulties in executing its core functions," such as dispute resolution and negotiations.

On the other side of the fence, the WTO has also been getting slammed for failing to rein in China for what the U.S. has repeatedly called its unfair trade practices.