AT 79, Wu Jinglian is considered China’s most famous economist.

In the 1980s and ’90s, he was an adviser to China’s leaders, including Deng Xiaoping. He helped push through some of this country’s earliest market reforms, paving the way for China’s spectacular rise and earning him the nickname “Market Wu.”

Last year, China’s state-controlled media slapped him with a new moniker: spy.

Mr. Wu has not been interrogated, charged or imprisoned. But the fact that a state newspaper, The People’s Daily, among others, was allowed to publish Internet rumors alleging that he had been detained on suspicions of being a spy for the United States hints that he is annoying some very important people in the government.

He denied the allegations, and soon after they were published, China’s cabinet denied that an investigation was under way.

But in a country that often jails critics, Mr. Wu seems to be testing the limits of what Beijing deems permissible. While many economists argue that China’s growth model is flawed, rarely does a prominent Chinese figure, in the government or out, speak with such candor about flaws he sees in China’s leadership.