SAN FRANCISCO (Reuters) - Google Inc was named on Monday in a trade secrets lawsuit alleging that the company's business software unit copied a tiny start-up's tool for moving customers off of Microsoft software onto Google's.

LimitNone LLC filed a complaint in an Illinois circuit court alleging that Google at first began promoting the smaller firm's tool for migrating Microsoft Outlook customers to Gmail, then copied the idea and went into competition with it.

The lawsuit was brought by the commercial litigation firm of Kelley Drye & Warren LLP -- by the same team who previously faced off with Google in a trademark case involving the Silicon Valley company's highly successful online advertising system.

The latest suit takes aim at the company's fast-growing Google Apps software application business, which includes Gmail for business users. Google is seeking to woo customers away from relying on rival Microsoft software.

The complaint accuses the Web leader of engaging in deceptive business practices that chill competition. It seeks reimbursement from Google of actual damages, attorneys' fees and calls on the court to award punitive damages to LimitNone.

Google was not immediately available to comment.

The case details LimitNone's meetings starting in March 2007 with Google to build a tool it called "gMove" for moving the e-mail, address books and calendars of corporate customers from Microsoft Corp's Outlook into Gmail. The suit alleges Google had trouble building a similar tool.

LimitNone said it entered a confidentiality deal with Google to share trade secrets of its e-mail migration tool with Google engineers, sales people and key Google Apps customers.

Last December, the firm of less than five employees learned from Google that it planned to enter the market for LimitNone's migration product itself because the business opportunity promised to be huge, according to court papers.

Lead plaintiff's attorney David Rammelt said in a phone interview that LimitNone had been told by Google that 50 million subscribers was "just too big to come from someone else" and that a simple calculation of the lost revenue for LimitNone "very quickly gets you up to about $950 million."

Google introduced a free, competing e-mail migration tool called "Google Email Uploader" earlier this year, which the lawsuit alleges is "almost identical" to gMove and that "both operate under a similar conceptual design."

Following Google's decision to compete with it, Palatine, Illinois-based LimitNone shifted its business to focus on the emerging market for business software designed to run on the Apple Inc iPhone.

Rammelt was lead attorney in the American Blinds trademark case against Google's AdWords online advertising system. The plaintiffs in that case dropped their suit last September, a few months before going to trial, citing mounting legal costs. Google declared victory in the four-year trademark battle.

(Editing by Braden Reddall)

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