Shares of HDFC Bank (HDBK.NS), opens new tab, ?India's top private lender, fell for a third straight session on Thursday, dragging the country's benchmark stock index amid concerns over legal, regulatory and leadership challenges.
The lender's shares slipped as much as 2.37% to their lowest in two and a half years, losing $2.6 billion in ?market value at close of trade.

The shares, down more than a quarter this year, are on course ?for their worst drop since 2008.

HDFC Bank is the largest stock by weightage on India's ?benchmark Nifty 50 index (.NSEI), opens new tab, which has fallen 7.8% this year.
The lender is facing a possible U.S. class-action lawsuit over ?alleged illegal payments worth 450 million rupees ($4.7 million) to Maharashtra State Road Development Corporation to induce large deposits.
On August 13, a ?couple of law firms filed a proposed federal securities class action in a U.S. District Court against HDFC Bank and two of its executives over the alleged illegal payments. Several other law firms have also issued alerts to HDFC Bank investors regarding the proposed ?class action.

"The U.S. class-action lawsuit has emerged as a near-term overhang, denting sentiment and tempering investor optimism despite the ?stock's attractive valuations," said Aishvarya Dadheech, founder and chief investment officer at Fident Asset Management.
"The Street is likely to remain cautious until ?further details ?emerge."
An HDFC Bank spokesperson told Reuters that the bank "believes the lawsuit is without merit and intends to vigorously defend itself."
"In the United States, these types of shareholder lawsuits are incredibly common after a company experiences a stock drop, and many companies listed in the U.S. routinely defend these lawsuits each year," the spokesperson said.
Earlier this week, Mint newspaper ?reported, citing investors, that more ?than 75 clients who bought ?Carlisle's Luxembourg Life Fund through HDFC Bank's Dubai operations were planning to approach the Indian Prime Minister's Office, the central bank and overseas regulators over alleged mis-selling, losses and ?delayed redemptions.

HDFC Bank told Reuters it does not provide any advice in relation to ?third party products ?and that it was ultimately for the customers to make their own informed decisions.

The lender's shares had slid in March after its part-time chair abruptly resigned citing ethical differences with management.
Uncertainty over chief executive Sashidhar Jagdishan's tenure also remains an overhang for ?the ?stock, traders said. Jagdishan's term ends on October 26.
A temporary extension would ?prolong succession concerns and could pressure the stock further, while a three-year renewal would remove a key uncertainty, Macquarie said.
The bank did not respond ?to a query on the CEO reappointment.