Economists inside and outside China have long warned that China is making little progress bringing down the country’s dangerously-high debt levels. Some official voices are now joining in.

"Corporate leverage, especially the debt ratios of state-owned enterprises, remains high," said Yang Kaisheng, a former top Chinese banker and now an adviser at the China Banking Regulatory Commission, at the annual conference of the China 50 Forum, which was founded by Liu He, President Xi Jinping's top economic adviser, and often conducts economic studies on behalf of China's policymakers.

Mr. Yang said even as the central government has made cutting debt a top economic priority in the past year, the economy's overall leverage ratios are going up, not down. In particular, he pointed out, as of the third quarter, debt-to-asset ratios at state-owned industrial companies ticked up to 61.5% from 61.2% a year earlier.

"It shows how difficult it is to reduce leverage," Mr. Yang said.

Overall credit has been growing faster than the Chinese economy since the 2008-09 global financial crisis—at a pace that has alarmed policy makers and investors around the world. Data released Tuesday show total social financing, a broad measure of credit in the economy that includes both bank loans and nonbank financing, reached a record 3.74 trillion yuan ($545 billion) in January.

As of the end of last year, total nonfinancial-sector debt stood at 277% of China's gross domestic product, according to a recent study by UBS Group AG, amounting to 205 trillion yuan. Of the 277% figure, UBS estimates that corporate debt accounts for about 164% of GDP, followed by a 68% as represented by government debt and the 45% by household debt.

A driving force behind the persistent credit surge is China's continued reliance on debt to fuel growth, which has led to an oversupply of unwanted goods and homes as well as a fast buildup of leverage.

At the economic conference Wednesday, some government advisers and economists acknowledged that the implementation of so-called supply-side reform—the term Beijing uses to describe its plan to cut overcapacity, debt and housing inventory—has been difficult in reality.

One issue policy makers face is "how to create a stable macro environment for reform to take place," said Chen Dongqi, a senior economist at a think tank affiliated with China's top economic planning agency, the National Development and Reform Commission.

In the past years, some researchers at the commission and elsewhere have urged China's central bank to aggressively loosen monetary policy to help lower funding costs for Chinese businesses. But instead of loosening, the People's Bank of China recently has shown a slight tightening bias in an effort to control asset bubbles as well as to steady the yuan.

At Wednesday's conference, held at a historic Beijing guesthouse, Mr. Yang, former president of the Industrial & Commercial Bank of China Ltd., suggested that regulators set specific leverage ratios for state companies. In the event of those ratios being met or exceeded, he said, the government should consider injecting capital into the companies.

But such a strategy should only be applicable to viable companies as opposed to money-losing “zombie” firms, Mr. Yang said. "Doing so can force the reform of state-owned enterprises."

--Lingling Wei