New Delhi, Jan 11 (PTI) The National Stock Exchange Friday said Ashok Chawla has resigned as chairman with immediate effect in light of recent legal developments.<br> However, the exchange did not provide specific details.<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. It was also investigating whether some brokers had unfair access to the exchange's co-location facility. <br> In a statement, the bourse said Chawla has resigned as "Public Interest Director/ Chairman of the Board of Directors of the National Stock Exchange of India Ltd with immediate effect in light of recent legal developments". PTI RAM<br> <br> <br> <br> MKJ