China's overall debt stood at 142 trillion yuan ($22.7 trillion), or 245 percent of GDP, as of March 31, Standard Chartered Plc estimated.

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That's up from 133 trillion yuan, or 233 percent of GDP, at the end of 2013, the bank said, noting that debt expansion slowed to 18 percent year-on-year during the first quarter, compared with 24 percent in the first three months of 2013.

Many foreign institutions have estimated the scale of China's debts using various calculation methods.

Standard Chartered has its own definition of debt, which is based on that of the central bank's "total social financing" concept, with some additional items.

It includes yuan bank loans, foreign exchange loans and entrusted loans (which are included in the calculation of 'total social financing'), as well as cross-border bank lending, offshore bond issues and other credits.

The slowdown of overall debt growth was particularly attributed to changes in foreign-currency bank loans, trust loans, undiscounted bank accepted drafts and outstanding corporate bonds, which slowed more than 50 percent year-on-year in the first quarter.

The bank said that the deceleration partly reflected China's deleveraging efforts, as well as higher interbank yields in the second half of 2013.