NEW DELHI: A Sebi panel has found the National Stock Exchange to have given preferential access to its co-location servers for algorithmic trading to some stock brokers, Parliament was informed on Friday."The architecture of NSE with respect to dissemination of Tick-by-Tick through Transmission Control Protocol (TCP) or Internet Protocol (IP) was prone to manipulation or market abuse," Minister of State for Finance Arjun Meghwal said in written reply to Lok Sabha.This system has been discontinued by NSE with effect from December 3, this year, he added.The Securities and Exchange Board of India (Sebi) had constituted an expert committee to examine the allegations of unfair privilege access given by NSE to some brokers for its ' algo ' trading.Algorithmic trading or algo in market parlance refers to orders generated at super-fast speed by use of advanced mathematical models that involve automated execution of trade while co-location involves setting up servers on the exchange premises.Quoting the Sebi committee's finding, the minister said: "Preferential access was given to stock broker(s), wherein it was possible for stock broker to log into multiple dissemination servers through multiple internet protocols assigned to him."It was also possible for a single member to have multiple logins to a single dissemination serve through multiple IPs assigned to it."It was observed that stock broker(s) had multiple advantage by logging in first or even second and third."To check on this malpractices, Sebi has directed stock exchanges to further strengthen the co-location facility in order to ensure fair and equitable access.In a separate reply, Meghwal said that Sebi found that companies which were either non-operational or had weak fundamentals and unsupportive price volume movements were being used by entities for price manipulation.During January-November, Sebi has passed orders in the case of 13 such companies and debarred 1,336 entities.Further, based on Sebi's direction, stock exchanges have also suspended trading in the shares of 203 companies. In addition, price bands of 160 firms were reduced to the lowest band of two per cent.