Axis Bank Ltd said on Monday that its long-time chief executive Shikha Sharma will step down at the end of 2018, days after Reserve Bank of India (RBI) reported to have expressed concerns about the lender giving her a three-year extension. India's banking sector has been facing increased scrutiny amid record-high bad loan levels within the banking system, the discovery of a $2 billion scam at state-run Punjab National Bank (PNB) and a slew of other issues.