At least 20 Irish stocks are due to come under closer scrutiny when data on short-selling in the Dublin market are published from the end of this month.

CrestCo, the company that oversees the electronic settlement of most trades on the Irish Stock Exchange, revealed yesterday that the publication of short-selling data would depend on a stock's market capitalisation.

Irish stocks will only be included in the analysis if they are larger or the same size as the 350 top companies listed on the London Stock Exchange.

As of yesterday, this list would have included 21 Irish companies ranging from the largest, AIB, to Tullow Oil at the edge of the range.

CrestCo business development manager Mr Jason Waight pointed out, however, that share-price fluctuations could see the constituents change before the Irish stocks are finally selected.

He also said that the extent of short-selling in a particular stock could influence its inclusion as a featured company. At least three short-sellers must, for example, be involved in a stock before any analysis of the activity will be published, with CrestCo planning to check this every day.

The company has judged that if a stock is targeted by any fewer than three players the publication of figures would be unfair, since it would lay the short-sellers' strategy bare before the market.

The service will initially be free but a charge will be levied after October 20th. The information will always be out-of-date by one week, again so that the strategies of short-sellers are not made immediately apparent.

Short-sellers usually trade by borrowing stock from a long-term holder at a fee and then selling the shares in the expectation that they will fall. The short-seller will then buy the stock back at the new price, return it to the original owner and net a profit.