National Stock Exchange today said Ashok Chawla has resigned as chairman with immediate effect in light of recent legal developments.  In a statement, NSE said Mr. Chawla has resigned as Chairman of the Board of Directors of the National Stock Exchange of India Ltd with immediate effect. However, the exchange did not provide specific details. <br />''<br />''The Securities and Exchange Board of India (Sebi) has been probing the alleged lapses in high-frequency trading offered through NSE's co-location facility. Ashok Chawla took charge as chairman of NSE in May 2016 from S B Mathur. Prior to joining the exchange,Chawla was the head of Competition Commission of India.