In a directive issued to national exchanges, FMC said: "The imposition of regulatory measures, like special margin/additional margin by the national exchanges at their discretion is observed to be creating lack of uniformity in the regulatory measures across the national exchanges.
"Hence, the National Exchanges are hereby directed to seek prior approval of the Commission before imposing additional/special margin," it said.
Commodities exchanges collect different types of margins (deposit money) by brokers and clients to avoid possibility of payment crisis in a falling market.
Special margins are usually imposed to check speculative activity in commodities trading.
There are four national commodities exchanges -- MCX, NCDEX, NMCE and ACE -- operating in the country.
