Security software vendor Symantec Corp. has complained to European Commission antitrust regulators about Microsoft Corp.’s entrance into the security business, setting the stage for a possible antitrust case against the Redmond, Washington, software company, the Dow Jones Newswire reported Thursday.

The “informal” complaint allows the Commission to consider whether or not an antitrust case against Microsoft is merited, said the report, citing unnamed sources. The Commission is the executive branch of the European Union (EU). European Commission officials could not be reached for comment late Thursday.

The news comes on the day Microsoft announced plans to begin offering business users an integrated antivirus and antispyware product called Microsoft Client Protection. A beta version of this product is expected to be released by year’s end. The company is already offering some customers a beta version of its Windows OneCare consumer security software.

At issue in the complaint is Microsoft’s plan to bundle its security software with Windows Vista, the next major version of the Windows operating system due next year, the report states.

Symantec spokeswoman Genevieve Haldeman said that her company had not filed a formal complaint with the Commission, but she stopped short of denying that an informal complaint had been made.

“We have been asked to provide information to the EU, and we have complied with that request,” she said. “The information was really helping them understand the complexity of the security industry and our role in it.”

“We have always said, and continue to say, that we’ll continue to compete with Microsoft in the market as long as there’s a level playing field,” Haldeman said.

Shortly after Microsoft announced its intention to enter the security space, Symantec Chief Executive Officer John Thompson hinted that his company was considering an antitrust complaint against Microsoft. “They can’t use their Windows monopoly unfairly, and the world will be watching. And we will as well,” he told IDG News Service in April.

Last year, the Commission ordered Microsoft to pay