San Francisco  - The Department of Justice has begun an antitrust investigation of whether IBM abused its monopoly in mainframe computers by unfairly denying access to competitors, according to an industry trade group that lodged a complaint with the government.

Ed Black, chairman of the Computer and Communications Industry Association (CCIA), said Thursday that members of the organization have received requests for information from the Justice Department regarding anti-competitive practices at IBM.

The CCIA said IBM denied licenses for its mainframe operating system to competitors who were trying to mimic the functioning of mainframes on cheaper servers.

Mainframe computers are designed to run large data intensive applications and according to the CCIA process over 80 per cent of computer-based transactions involving ATM sessions, airline bookings, tax filings, health records and other essential services. IBM's operating system is the de facto industry standard for such computers, the CCIA claimed.

"IBM has exploited its monopoly in mainframe operating systems to keep its customers 'locked in' to the IBM mainframe platform," Black said. "IBM has in fact had a monopoly for decades."

In a statement, IBM said it was aware of the investigation, but believed that "IBM is fully entitled to enforce our intellectual property rights and protect the investments that we have made in our technologies."  dpa