European authorities took an even more aggressive approach than usual to regulating the technology industry Wednesday when they applied a rarely used rule, ordering a company to halt a potentially anticompetitive practice while an investigation is underway.

The European Commission’s top antitrust enforcer, Margrethe Vestager, said “interim measures” were being taken against the company, the chip maker Broadcom, to ensure that its competitors were not marginalized amid an inquiry. It is the first time the regulator has used the rule in nearly two decades, signaling urgency within Europe to keep the technology market competitive.

Broadcom, the leading maker of chips used in television set-top boxes and modems, has been accused of using exclusivity agreements to block customers from using products made by rivals. A formal inquiry of Broadcom was opened in June, and the European Commission is now ordering the company to stop enforcing the exclusionary terms with six manufacturers of the boxes and modems.

Ms. Vestager said Broadcom’s competitors would lose revenue and viability if the company’s actions were not halted, and that spurred her decision. “They will progressively be marginalized and may ultimately be forced to leave the market,” she said.