As a first major step to tighten listing norms, the Bombay Stock Exchange is set to slap notices on over 100 companies whose share trading remains suspended for over six months.

The premier stock exchange also plans to make disclosure norms stringent to prevent "back-door entry" of unlisted companies, official sources said on Tuesday.

"We have constituted a committee for short-listing the companies which were not complying with our listing norms and were not friendly towards the investors. The exchange will start sending notices to these companies in phases from next month," a BSE official said.

There are over 2,500 companies whose shares were suspended from trading for over six months. Many of these companies did not pay any listing fees or comply with other listing norms.

"Many companies did not utilise initial public offering proceeds for the projects for which they raised funds," the official said.

BSE intends to slap notices on about 100 companies in the first phase, the official said.

The Securities and Exchange Board of India has earlier taken stringent steps against companies which mopped up resources from the market and then vanished.

"There have been cases of back-door entry of unlisted companies by way of acquiring a smaller listed entity. There is no way we can prevent listing of such companies," the BSE official said.

The listing norms would be made uniform once Sebi comes up with the Central Listing Authority.

Once it comes up, all companies willing to list their shares on Indian bourses would have to get clearance from the CLA and then list on the bourse of their choice.

To safeguard investor interest, BSE also plans to come up with a standard system for reverse book-building to fix the share price of companies opting for delisting.

The exchange is ready with its demutualisation scheme, which has been submitted to SEBI, the BSE official said.

Of the total 18 board members, the exchange would induct six broker representatives, six from shareholders and the remaining would be allocated to public representatives.

The government is in the process of bringing in a bill to amend the Securities Control Regulation Act to pave the way for demutualisation of bourses.