Microsoft has stepped up its rivalry with Google by filing a lawsuit against the search company over the hiring of a former Microsoft employee.

In a complaint filed in the King County Superior Court in Washington, Microsoft alleges that Kai-Fu Lee, who joined Google to spearhead new research and development efforts in China, is violating a non-competition agreement signed when he was hired at Microsoft. Until Monday, Lee was corporate vice president of Microsoft's Natural Interactive Services Division.

"We are asking the Court to require Dr Lee and Google to honour the confidentiality and non-competition agreements he signed when he began working for Microsoft," the company said. "Creating intellectual property is the essence of what we do at Microsoft, and we have a responsibility to our employees and our shareholders to protect our intellectual property. As a senior executive, Dr. Lee has direct knowledge of Microsoft’s trade secrets concerning search technologies and China business strategies. He has accepted a position focused on the same set of technologies and strategies for a direct competitor in egregious violation of his explicit contractual obligations."

Among other things, Microsoft is asking the court to prevent Lee and Google from undertaking any actions that violate Lee's non-compete employment agreement with Microsoft, as well as from "disclosing or misappropriating" any of Microsoft's trade secrets or proprietary information, according to the complaint.

Microsoft also is requesting that the court to prohibit Lee or anyone at Google from possibly luring other Microsoft employees away from the company, as well as from destroying any documents, whether written or electronic, that relate in any way to Microsoft's and Google's employment of Lee.

In a statement, Google executives said Microsoft's claims are "completely without merit" and that the company plans to fight the suit.

"We're thrilled to have Dr Lee on board at Google," the company said. "We will defend vigorously against these meritless claims and will fully support Dr. Lee."

Google and Microsoft have become increasingly heated rivals in the areas of e-mail and desktop search, and Microsoft Chief Executive Officer Steve Ballmer has repeatedly expressed his intentions to unseat Google from its dominant position in the search engine space. Indeed, just this Monday, Microsoft Chairman and Chief Software Architect Bill Gates referred to Google as a "faddishly hot" company, suggesting that the vendor is merely a flash in the pan.

It's not uncommon for technology companies to require employees to sign so-called non-compete agreements that prohibit them from working at a competitive company or luring other employees away from their previous employers for a certain time period after they terminate their employment.

This is not the first time Microsoft has taken legal aim at former employees based on such agreements. One highly publicised case in 2000 involved the vendor suing former employees Tod Nielsen, Adam Bosworth and others for violating non-compete agreements when they left the company to form a new software company, CrossGain.

The suit eventually caused former Microsoft employees working at CrossGain to take a hiatus from the company until their one-year non-compete agreements expired, but they eventually returned the startup.

Google hopes that Lee, who is known for his work in the areas of speech recognition and artificial intelligence, will expand Google's recruitment, research and development efforts in China. The vendor expects to open its new China facility in the third quarter of this year.