Google is being sued for $1bn by a technology start-up which claims that the search giant stole a migration tool it had developed.

LimitNone said that Google initially distributed its gMove tool for migrating users of Microsoft's Outlook to Gmail.

However, the firm claims that Google then introduced its own tool, Google Email Uploader, which is virtually identical to gMove.

"LimitNone alleges that Google's software program is essentially identical to LimitNone's product and that Google could not have developed its competing product without using the information it learned from having access to and studying LimitNone's confidential and proprietary program," said LimitNone attorney David A. Rammelt.

"The complaint alleges that Google's own executives predicted that the migration tool would have '50 million users' which, in the end, proved too great a temptation for Google."

The papers allege that Google executives told LimitNone in a telephone conversation that a market of that size would be worth around $950m in revenues and that, as such, it was too much money for Google to pass up.

LimitNone, which has five employees, claims that it was forced out of the market.