The groups released a report responding to criticism from some of the company's largest rivals, including Oracle and Sun Microsystems, that charged Microsoft intends to use its new Windows XP operating system and Microsoft.Net Web services strategy to force its technologies on Internet users.
The two groups backing Microsoft--the Association for Competitive Technology and the Computing Technology Industry Association--said the company's competitors are the ones truly stifling competition.
Microsoft competitors "would twist antitrust laws to stop Microsoft from developing integrated software," the groups said in the report.
With a federal appeals court about to release a decision on the landmark antitrust ruling against Microsoft, the software company, its rivals and each side's backers have been slugging the issue out in the court of public opinion.
Some legal experts have predicted that the U.S. Distirict Court of Appeals will overturn much of the ruling against Microsoft, including the order to break the company into two entities. In such a scenario, the Justice Department would probably settle the case, with Microsoft staying intact and facing far fewer restrictions on its business practices.
Microsoft's foes struck first this month as they tried to persuade the Bush administration to preserve a lower court's ruling.
Procomp, the group funded by Microsoft competitors, said in a May 17 report that the Microsoft.Net strategy is an attempt to "turn the Internet into a big Microsoft subscription service."
"When consumers start Windows XP, therefore, (they) will have precisely one browser, one e-mail product, one media player, one instant-messaging program," the Procomp report said.
Under Microsoft.Net, the company plans to charge subscription fees for some of its consumer software and services, such as instant messaging.
The groups backing Microsoft called the accusations that Microsoft.Net is a tool to throw a stranglehold around the Internet "paranoid."
".Net and its component software products have yet to be released," Wednesday's report said. ".Net is precisely the type of risk-taking investment and competitive initiative encouraged by the antitrust laws."
Reuters contributed to this report.