The IMF, in its latest Global Financial Stability report, analyzed the effect of years of exceptionally low interest rates and bond buying by these central banks since the global financial crisis.
While noting these bold actions by the central banks have reduced the banking sector's vulnerabilities and stabilized interbank and mortgage securities markets, the report said such policies may also produce undesirable side-effects that could put financial stability at risk the longer they remain in place.
The IMF said thus far such risks have not shown up in banks. However, it said, there is some concern the prolonged period of low interest rates is encouraging banks to roll over non-performing loans instead of fixing their balance sheets.
"So far so good, but if the time that central banks have provided through their unconventional policies is not used productively by financial institutions and their regulators, at some point we can expect another round of financial distress," said Laura Kodres, who headed the report team at the IMF's monetary and capital markets department.
The analysis said delay in balance sheet repair at banks could raise credit risk over the medium term.
Risks may also be shifting to other parts of the financial system such as pension funds and insurance companies -- or to other countries, the report said, adding some of the risks may crop up when the central banks end their policies.
The report said central banks should continue to support the economy and financial stability until the recovery is well established but asked policymakers to remain vigilant for any emerging financial stability threats.
Robust capital requirements and improved liquidity requirements were among other measures suggested by the IMF to contain credit risk and funding challenges for banks.