MADRID/BARCELONA, Jan 9 (Reuters) - Shares in Grifols fell by 30% on Tuesday, wiping nearly $3 billion off its market value, after hedge fund Gotham City Research questioned its accounting, prompting the Spanish drugmaker to "categorically" deny any wrongdoing.

Gotham questioned Grifols' reported debt and earnings before interest, taxes, depreciation and amortization (EBITDA), and leverage ratio of 6.7 times. It said the leverage ratio is close to 10 to 13 times EBITDA.

Grifols, which makes medicines with human plasma, said in a filing to Spain's CNMV stock market supervisor that the Gotham report was "false information" and "speculation." The company had disclosed information about all the transactions raised "with the highest level of integrity and transparency," it said.

CNMV head Rodrigo Buenaventura said it made "no sense to question the integrity of the audited accounts" of Grifols or to ignore the "very serious accusations" made by Gotham.

"What we at the CNMV have to do is gather additional information to clarify the situation and see which aspects of the information need to be reviewed or analyzed," he added.

Board member Tomas Daga, who sits on Grifols' audit committee and has advised it as a lawyer on several acquisitions, told Reuters a crisis committee had met on Tuesday and there would be a board meeting in the afternoon.

"Our house is clean, we are very sure about that. We will explain it again point by point," Daga said.

He described the fund's report as an act of "despair" after Grifols last month sold a 20% stake in Chinese unit Shanghai RAAS for $1.8 billion to cut its debt, while Gotham had bet on no deal.

Daga said it was in Gotham's interest for the company's share price to fall since it and its partners hold short positions of more than 0.5% in Grifols, meaning the fund stands to profit in the event the stock declines.

Active short-sellers like Gotham, which bet on share price falls, can wipe huge sums off the market value of their targets.

Shares in Grifols, which dropped 42% at the market open, were down about 26% in late afternoon trading in Madrid and in early trading on Nasdaq.

KPMG, which audited Grifols' 2022 accounts, did not respond to requests for comment.

Banco Sabadell analysts said that although the allegations will weigh on Grifols' share price, particularly from an environmental, social and governance (ESG) perspective, it would be not changing its valuation until it was certain whether any mistakes had been made.

SHORT SELLER

Gotham was founded by Daniel Yu and focuses on "due diligence-based investing." On its website, it said it has long or short positions in the companies it reports on.

The fund has targeted online advertising company Criteo and Apple-supplier AAC Technologies and more recently French smart labels maker SES Imagotag.

Another target, Let's Gowex, later filed for bankruptcy.

Last year, another short-seller Hindenburg Research triggered a $150 billion selloff in Adani Group shares, even though the Indian company denied any wrongdoing. Last week, India's Supreme Court said the group does not need to face more investigations beyond current scrutiny by its market regulator.

Grifols shares have swung widely over the past few years as the company, whose market value peaked at 20.75 billion euros in February 2020, was hit hard by the pandemic when plasma collection was restricted.

The company has sought to reassure investors with cost-cuts and a leadership change, lifting its shares by 43% in 2023.

Grifols' October 2028 bond fell sharply after Gotham's report and was down 7.8 cents on the day at 82.98 cents on the Marketaxess platform.

The company faces two large debt maturities in the first half of 2025 totalling about 1.85 billion euros, according to Moody's credit rating agency.

Daga said Gotham's allegations "should not affect at all" Grifols' financing needs, and saw no need to refinance until late 2026, with the 2025 maturities covered by the Chinese sale.

(Reporting by Inti Landauro and Joan Faus, additional reporting by Emma Pinedo, Jesus Aguado, Amanda Cooper and Matteo Allievi; Editing by Sharon Singleton and Alexander Smith)