A US software industry group attempted to intervene in the Microsoft antitrust lawsuit yesterday, by demanding to testify before courts on the impact of the proposed break-up of the world's largest software company.

The Association for Competitive Technology (ACT) filed a motion in court asking the trial judge in the landmark case to allow its members to describe the harm they would suffer under Microsoft's break-up.

The motion cites the case of small companies which already claim to have suffered because of the Justice Department's request to split Microsoft in two.

The Justice Department and 19 states, which are jointly suing the company, are scheduled to reply today to Microsoft's own `remedy` proposals, following the company's outright rejection of the break-up request last week. Microsoft offered instead to curb its business practices, claiming that break-up would cause unpredictable damage to the US economy.

According to ACT's motion filed yesterday, Active Designs, a small systems integrator from Fairfax, Virginia, claims to have lost business because of uncertainties over Microsoft's future. The company claims that a customer is delaying its deployment of Microsoft's Windows 2000 software based on concerns over the future of the Windows operating system.

Mr Jonathan Zuck, president of the ACT, said the legal precedent for widespread consultation had been set by the agreed break-up of AT & T, the telecommunications company, in the early 1980s. Under the so-called Tunney Act, the courts must give at least 60 days' notice for public comment before a proposed settlement can be approved.

"Our feeling is that the implications are so much greater than the AT & T case," he said.

The association has consistently backed Microsoft throughout the course of the two-year litigation, and strongly opposes breaking up the company.