U.S. credit rating agency Standard & Poor's said Wednesday that it has downgraded Japanese electronics company Toshiba Corp.'s long-term corporate credit to "BBB-" from "BBB," stating that confusion in its operations arising from "inappropriate" accounting may continue to have a negative impact on its earnings.

The outlook for the company is "negative," S&P said, maintaining its view of downside risk in Toshiba's earnings and financial performance in the next one to two years.

Toshiba, which produces a diversified range of products from consumer electronics to infrastructure systems, disclosed on Monday its last fiscal year earnings after the revelation of overstated profits and other irregular accounting practices forced reporting delays.

The company, listed on the Tokyo Stock Exchange, announced a group net loss of ¥37.83 billion ($312 million) for fiscal 2014, a huge turnaround from ¥60.24 billion in profit a year earlier.