The top executive of Japan's biggest bank delivered a rare criticism of the central bank on Thursday, saying its negative-interest-rate policy has contributed to anxiety among households and companies and prolonging it may weaken financial institutions.

"Both households and businesses have become skeptical about the effectiveness of policy measures to address the current economic problems," Nobuyuki Hirano, president of Mitsubishi UFJ Financial Group Inc., said in a speech in Tokyo. Declines in banks' net interest margins "will become even more severe and protracted by the implementation of the negative-interest-rate policy," he said.

Hirano said there is "no guarantee" that negative rates will encourage companies to increase capital spending because low borrowing costs and deflation have been "business as usual for over a decade." Lenders won't be able to pass on negative rates to individual and corporate depositors, he said in English at a conference of international bankers.

His remarks are among the strongest yet by a banking executive following the Bank of Japan's decision in January to start charging lenders on some of their excess reserves to spur credit growth and investment. BOJ Gov. Haruhiko Kuroda said in New York late Wednesday that Japan's financial markets would have been in worse shape if the BOJ did not introduce the policy and that there is room for further rate cuts.

So far, the policy has yet to spur bank lending, which rose the least in three years in March, BOJ figures showed this week. The average interest rate on new loans fell to a record-low 0.793 percent in February.

Mizuho Financial Group Inc. Chief Executive Officer Yasuhiro Sato said in a speech Wednesday that the policy needs to spur a positive economic cycle and that it will take time to bear fruit.