New Delhi, March 27 -- The market regulator has proposed limiting the expiry of derivative contracts to either Tuesdays or Thursdays, a move that could upset the National Stock Exchange's (NSE) plan to shift the last day for its weekly index option to Monday.

The proposed move is aimed at minimizing concentration risk and allowing product differentiation, according to a consultation paper released by the Securities and Exchange Board of India (Sebi) on Thursday. The paper seeks to formalize the final settlement days for derivative contracts across exchanges and avoid any unwarranted shuffling.

"Every exchange will continue to be allowed one weekly benchmark index options contract on their chosen day (Tuesday or Thursday)", the paper sai...