NTP filed a patent infringement lawsuit against Palm, echoing the allegations the patent-holding firm made that nearly shut down Research in Motion's (RIM's) BlackBerry service.

The new lawsuit, filed Monday in the U.S. District Court for the Eastern Region of Virginia, alleges that Palm is using NTP technology in its mobile wireless e-mail devices, and asks the judge to stop Palm from selling and operating such products, and to fine the company for punitive damages.

Palm's Treo 600 and 700 series smartphones combine phone service, e-mail and Internet access in a single handheld device. Treo sales are a primary reason for Palm's success, generating more than half the company's annual revenue.

NTP claims it filed this lawsuit as a last resort, after failing to negotiate a license agreement in previous talks, according to a statement from NTP co-founder Donald Stout. The company has licensed its wireless e-mail technology to device makers such as Good Technology, Nokia and Visto.

Palm responded that it has been in occasional contact with NTP to discuss licensing the patents. It last communicated with NTP "many months ago," around the time that each of the relevant patents was being re-examined by the U.S. Patent and Trademark Office. The patent office has found the patents invalid but is still in the midst of a potentially lengthy re-examination process.

"Palm respects legitimate intellectual property rights, but will defend itself vigorously against the attempted misuse of the patent and judicial systems to extract monetary value for rights to patents that may ultimately have no value at all," the company statement.

Palm said the NTP patents cover an e-mail system that uses pager technology, a method that Palm said has nothing in common with its own technology.

In March, RIM agreed to pay US$612.5 million to settle NTP's patent claims and gain the right to continue its smartphone business. The threat of an injunction had pulled many bystanders into the case, even pushing the federal government to argue before the judge that shutting down BlackBerry service would stop many federal employees from doing their jobs.

Nancy Gohring in Dublin contributed to this report.