India's HDFC Bank said late on ‌Wednesday that its part-time chairman, Atanu Chakraborty, had resigned citing differences with the ​lender over "values and ethics", and appointed insider Keki Mistry as interim part-time chairman.

U.S.-listed ​shares of ​HDFC Bank, India's largest private-sector lender, slipped 7% following the announcement. Its Mumbai-listed shares had closed 0.3% lower before the ⁠news on Wednesday.

"Certain happenings and practices within the bank, that I have observed over last two years, are not in congruence with my personal values and ethics," Chakraborty said in his resignation letter, ​without elaborating.

"The ‌RBI should be ⁠on top ⁠of the issue as HDFC Bank is a systematically important bank. But since ​the RBI has appointed a group insider ‌Keki Mistry in his place it ⁠could mean less alarm for shareholders" said Amit Tandon, chief executive, Institutional Investor Advisory Services, a proxy advisory firm, which counts HDFC Bank among its shareholders.

Chakraborty was appointed as part-time chairman in April 2021 for a three-year term and reappointed in May 2024 through May 4, 2027.

During his tenure, HDFC Bank merged with housing finance firm HDFC Ltd in a $40 billion deal, creating ‌a financial services behemoth.

In his resignation letter, Chakraborty noted ⁠that benefits of the 2022 merger were "yet to ​fully fructify".

The RBI has approved the appointment of long-time group insider Keki Mistry as an interim part-time chairman for three months, effective ​March 19, ‌the bank said in its filing.

(Reporting by Chris ⁠Thomas in Mexico City; ​Editing by Shilpi Majumdar, Shailesh Kuber and Sumana Nandy)