A Bank of Japan board member warned of potential dangers if the central bank's already massive stimulus is ramped up, a view suggesting there is no consensus on how quickly it should ease policy again to head off the risk of recession.

Hitoshi Suzuki, a former commercial banker turned BOJ policymaker, said further declines in borrowing costs would do more harm than good as financial institutions might mitigate the pain by charging fees on households' deposits.

"If bank deposit rates effectively turn negative, it could hurt the economy by cooling consumer sentiment," Suzuki told.

Excessively low interest rates would also discourage financial institutions from lending and diminish the impact of monetary easing, he added.

"Once the financial system destabilises, it will become very difficult to achieve price stability," he said, stressing that the BOJ needed to pay more attention to the health of Japan's banking system in guiding monetary policy.

Suzuki's remarks underscore a rift within the nine-member board that could make it hard for Governor Haruhiko Kuroda to meet his pledge to ease policy "without hesitation" to underpin the economy's recovery.