Toshiba Corp.'s bonds were Japan's biggest losers this month, and the worst may not be over in the nation's latest accounting scandal.

The company's 1.68 percent debt maturing in 2020 lost 1.45 percent in July, the most among 621 yen-denominated corporate issues in a Bank of America Merrill Lynch index.

Standard & Poor's said last week it may cut Toshiba's BBB rating, the second-lowest investment grade.