A lawsuit seeking class action status has been filed against WiMAX operator Clearwire.

The suit alleges that the company falsely touts its mobile WiMAX network as a reliable “always-on” alternative to cable or DSL Internet access and traditional wireline phones and imposes unlawful early termination fees when the promised service is slow, unreliable or unavailable.

Clearwire could not be reached for comment by press time.

The complaint accuses Clearwire of falsely advertising its Internet and phone services, alleging that Clearwire’s phone service is “far inferior to traditional landline service, as subscribers experience frequent service disruptions.” The suit also alleges that Clearwire’s early termination fee is unlawful and stymies competition.

Customers in several states where Clearwire offers fixed service are among the plaintiffs, including people in Washington, Hawaii, Minnesota and North Carolina. They seek to recover the early termination fees they have paid, as well as an injunction prohibiting Clearwire from enforcing the fees and falsely advertising its service.

The suit, Minnick et al. v. Clearwire US  LLC, was filed in King County, Washington. Plaintiffs are being represented by Washington, D.C.-based firm Tycko & Zavareei LLP and the Seattle law firm of Peterson Young Putra.

Multiple consumer complaint Web sites have sprung up against Clearwire. The sites allege that Clearwire’s service is spotty, slow and unreliable and contain complaints about equipment failures, billing problems and poor customer service.

Clearwire plans to spend from $1.5 billion to $1.9 billion in 2009 to build out its mobile WiMAX network, expanding its network to cover 120 million people in 80 markets in 2010. In January, Clearwire launched its mobile WiMAX service in Portland, Ore. after Sprint launched its first mobile WiMAX market in Baltimore, Md., last year.