The legal team at Vonage Holdings Corp. (NYSE: VG) can forget any plans for a peaceful holiday season.

Having worked overtime to fend off a number of patent lawsuits already this year, the VOIP service provider has attracted yet another patent infringement challenge, this time from Nortel Networks Ltd. .

In an email to Light Reading, following a number of media reports over the weekend, Nortel says it is "seeking damages and a permanent injunction against Vonage around the use of our technology."

Nortel states:

We pride ourselves on our technology leadership in building the foundation on which commercial VoIP rests. The patents cover fundamental elements of the architecture of the Vonage network and many of the most popular features of the Vonage service, including 911, 411, click to call, and other technologies related to their commercial VoIP architecture.

Vonage has already settled three patent lawsuits this year, with AT&T Inc. (NYSE: T), Sprint Corp. (NYSE: S), and Verizon Communications Inc. (NYSE: VZ). (See Vonage Posts Q3 Loss, Settles With AT&T, Vonage Settles With Verizon, and Vonage Soars on Sprint Settlement.)

Nortel's action spells further bad news for Vonage's investors, who have seen the VOIP firm's share price head south since its IPO in May 2006. The company sold its stock at $17, but its share price fell from day one and currently stands at $2.05. (See Vonage Falls Hard & Fast in Public Debut, Vonage Gets a Haircut, Vonage Class Action: What's the Damage? , Regulators, Lawyers Swarm Vonage, and Poll: Vonage IPO Gets Thumbs Down.)

Vonage had not returned calls for comment as this article was published.

— Ray Le Maistre, International News Editor, Light Reading