Scandal-hit Toshiba Corp. apologized Friday for not disclosing the massive impairment loss of U.S. nuclear power plant maker Westinghouse Electric Co. and vowed to be committed to more proactive information disclosure.

Earlier this month, weekly magazine Nikkei Business reported that Toshiba did not disclose the write-downs of Westinghouse's nuclear business in fiscal 2012 and 2013.

Following the report and under pressure from the Tokyo Stock Exchange, Toshiba revealed on Nov. 17 that it saw write-downs of Westinghouse's value totaling around ¥115.6 billion in the two years.

The outlook for Westinghouse's nuclear business became murky after the March 2011 Fukushima disaster.

"We are deeply sorry and should have disclosed the information earlier at an appropriate time," Toshiba President Masashi Muromachi said at a news conference at Toshiba's headquarters in Tokyo.

"From now on, I will lead efforts to more actively disclose information to regain the trust," he said.

Toshiba said it is conducting its asset evaluation based on the Generally Accepted Accounting Principles (GAAP) in the U.S. It said it was not aware that posting the Westinghouse impairment loss in Toshiba's group business results was necessary at the time.

But Toshiba flip-flopped after the TSE took issue, saying it was necessary to disclose the impairment losses for fiscal 2012 as a TSE rule states a company must disclose a subsidiary's losses when they exceed 3 percent of the group's net asset.

Toshiba bought Westinghouse Electric Co. in 2006 and evaluated its goodwill at about ¥350 billion.

This is another blow to scandal-tainted Toshiba, which is trying to let an accounting scandal blow after padding net profits by a staggering ¥152 billion between fiscal 2009 and 2014.