The attorney general of Connecticut has launched a lawsuit against Vonage Holdings Corp, alleging that the company has misled consumers over the limits of 911 emergency calls.

Emergency calling for consumers who use Voice Over Internet Protocol (VOIP) services has become a top concern among federal and state regulators, and a growing headache for Vonage, the largest independent VOIP provider.

Calls to 911 with traditional telephones provide emergency service dispatchers with the caller's number and address. VOIP providers have limited access to the systems connecting those calls to emergency dispatchers, and typically route calls to office numbers that are not always answered.

In this case, it has been claimed that a customer in Connecticut who dialled 911 for a medical emergency reached a recording. Therefore, the attorney general claims that Vonage misrepresents its 911 services; such calls may take a long time to be answered, or may not be answered at all. The suit seeks changes in Vonage's marketing as well as financial penalties which have as yet not been specified.

Vonage spokeswoman Brooke Schulz said the Connecticut customer had activated her 911 service, and was given "full disclosure" about its limitations.

"We're always willing to look at improvements to our disclosures, but the ultimate improvement is access to the 911 network," Schulz said. "We really need to focus on the root of the issue."