In a simmering legal tussle, Google Inc. has asked a judge to reject Microsoft’s bid to keep a prized research engineer from taking a job at the Internet search company, saying the software titan filed its lawsuit to scare other employees out of defecting.

Microsoft sued Kai-Fu Lee, one of its former executives, and Google last week, claiming that by taking the Google job, Lee was violating an agreement he signed in 2000 barring him from working for a direct competitor in an area that overlapped with his role at Microsoft.