A meeting of the core group on depositories is being convened to take a decision to this effect and shortlist the securities which will take the number of scrips where institutions are required to trade in demat shares only, to 100, said Sebi chairman DR Mehta.

Speaking to The Financial Express, Mehta said that the list of securities will be announced in one go but the deadlines for commencing compulsory trading would be in two tranches -- one in October and another in December.

"We want to send a clear message to the market that we are all for dematerialisation. We will therefore announce all the 50 stocks shortly so that the market can prepare itself for the move well in time," Mehta said.Most of the top securities comprising the Nifty and Sensex indices have already come into the fold of compulsory demat forinstitutions.

The first list of eight securities was announced on November 15, 1997, and came into effect in January 15 this year. The second list of 22 securities was announced on April 24 and came into effect from June 1 onwards. The third list of 20 securities was announced a fortnight later and comes into effect from August 10 onwards.

Reliance, State Bank of India, Tisco, IDBI, Bank of India, ICICI, IPCL, L&T, Telco, BSES, ACC, HPCL, Tata Chemicals, Gujarat Ambuja, HLL, M&M, Infosys, Great Eastern Shipping, HDFC, HDFC Bank, Hindalco, BPCL, Arvind Mills, Dr Reddy's Laboratories, Indian Hotels, Grasim, VSNL, Castrol, Crisil and Ranbaxy are the securities where institutions are currently mandated to trade only in demat form.

These will be followed on August 10 by ABB, Asian Paints, Cochin Refineries, Glaxo India, IFCI, Indo-Gulf Fertilisers, Indian Rayon, MRPL, Oriental Bank of Commerce, Reliance Capital, Reliance Petroleum, Sail, Tata Tea, Thermax, TVS Suzuki, Bajaj Auto, ITC, Hero Honda, MadrasRefineries and NIIT.

The depository has received a major boost over the past few months since the Sebi mandated institutions to trade only in the demat form as also decided to allow shares to be delivered in the physical segment of stock exchanges as well.