* Filing extension moves deadline to Aug 10
* Investigation ongoing over accounting at bankrupt nuclear unit
* President Tsunakawa to hold news conference 0800 GMT
* Toshiba flags deeper net loss for last FY on potential damages
* Toshiba scrambling to sell memory chip unit to get needed cash (Recasts with stock listing downgrade, bigger losses and filing extensions)
TOKYO, June 23 (Reuters) - Crisis-wracked Toshiba Corp suffered further indignities on Friday, estimating bigger losses for the past financial year and getting demoted to the second section of the Tokyo Stock Exchange.
It also received regulatory approval to delay filing its annual earnings by more than a month amid a prolonged accounting investigation at its bankrupt Westinghouse nuclear unit. It is the sixth time since 2015 that Toshiba has delayed an earnings filing.
Underscoring the firm's dire financial position that has forced it to sell off its highly prized chip unit, Toshiba said it now estimates it had a worse-than-expected negative shareholders' equity of around $5.2 billion as of end-March.
With negative shareholder equity confirmed, the Tokyo Stock Exchange said it would move Toshiba's listing to the second section of the bourse from Aug. 1.
Regulators have now given Toshiba until Aug. 10 instead of June 30 to make its earnings filing. Failure to gain an extension would have put the troubled company's stock exchange listing in further jeopardy.
Toshiba President Satoshi Tsunakawa will hold a news conference at 5 p.m. Tokyo time (0800 GMT).
The firm has been on the Tokyo bourse's supervision list since mid-March as it has failed to clear up concerns about its internal controls after a 2015 accounting scandal. It still needs to dig itself out of negative shareholders' equity by the end of this financial year to stay listed.
Toshiba also estimated a net loss of 995.2 billion yen for the past financial year, bigger than a previous estimate of 950 billion yen, as it braces for potential damages over an accounting scandal as well as an increase in liabilities Westinghouse.
Toshiba this week chose a consortium of Bain Capital and Japanese government investors as the preferred bidder for its flash memory chip business, aiming to seal a deal worth some $18 billion by next week.
But prospects for a clean early resolution to the sale of the world's No. 2 producer of NAND flash chips remain unclear as Western Digital Corp, Toshiba's chips business partner, has launched legal action to prevent a deal without its consent.
($1 = 111.2500 yen) (Reporting by Makiko Yamazaki and Kaori Kaneko; Editing by Chang-Ran Kim and Edwina Gibbs)