Aug 25 (Reuters) - Hawaiian Electric shares slumped 22% before the bell on Friday as the utility suspended its dividend, while S&P Global Ratings downgraded its credit rating deeper into "junk" territory amid scrutiny over its role in the Maui wildfires.

The Honolulu-based company is also being sued by the Maui county which has alleged that it acted negligently by failing to shut down power, leading to wildfires that destroyed the coastal town of Lahaina and killed more than 114 people.

"We are very disappointed that Maui County chose this litigious path while the investigation is still unfolding," the company told Reuters. It had previously said shutting off power was not part of its high-wind management protocol.

S&P Global Ratings cited the utility's likely inconsistent access to capital markets after the wildfire to downgrade the firm and its units to 'B-' from 'BB-', its second ratings cut this month.

The largest power supplier in the island state said it would invest $200 million that it withdrew from its credit account in highly liquid assets along with the $170 million drawn by parent Hawaiian Electric Industries to shore up its balance sheet.

Moody's and Fitch had also downgraded Hawaiian Electric to junk status in August.

Hawaiian Electric's market value has slumped more than 60% to $1.30 billion since the Aug. 8 wildfire. The stock is trading 5.6 times its forward earnings estimate, well below its 2023 peak multiple of 18.4, according to Refinitiv data.

(Reporting by Medha Singh in Bengaluru; Editing by Arun Koyyur)