The Bank of Japan may need to expand its purchases of corporate debt to prevent a credit shortage from worsening the recession, BOJ Deputy Gov. Hirohide Yamaguchi said.

"We can't deny corporate financing will become even more difficult" toward the fiscal yearend on March 31, Yamaguchi said Thursday in Tokyo in his first interview since joining the board in October.

Yamaguchi is the first member of the board to hint at further policy actions since it unveiled the plan to purchase corporate bonds from banks last month. Having cut interest rates close to zero, the central bank is buying assets to channel funds to businesses whose profits are falling the most in more than 30 years as demand dries up at home and abroad.