The Reserve Bank of Australia (RBA) Governor Glenn Stevens said in a speech on Tuesday that central banks' inability to boost the global growth was the biggest risk to the global financial system.

"Our inability, so far, durably to lift growth prospects is arguably the biggest vulnerability the global financial system faces today. This needs to be our focus," he said.

Stevens also said that ultra-low interest rates for a longer period was a big problem for savers.

Referring to helicopter money, the RBA governor noted that it was easier to start doing helicopter money than to stop.

"Desperate times call for desperate measures, perhaps. Are we that desperate?" he added.