An association representing major cruise lines operating in Alaska on Friday filed a lawsuit against the state of Alaska seeking to overturn the state's passenger head tax, a levy the cruise companies claim is unconstitutional and has stifled business.

The lawsuit, filed in U.S. District Court in Anchorage, argues that $46 of the state's $50-per-passenger head tax violates the U.S. constitution because it unduly interferes with maritime and interstate commerce.

We feel the entry fee, as implemented, is illegal. Alaskans are being hurt by the tax and the court system is really the best venue to resolve the issue, said John Binkley, president of the Alaska Cruise Association.

The association represents nine member companies, including Carnival Corp, Royal Caribbean Cruises Ltd, Norwegian Cruise Line and others.

The tax was imposed as part of a wide-ranging cruise ship initiative passed by Alaska voters in 2006 that also included new environmental regulations.

Cruise companies and operators of various tourism companies that cater to cruise passengers have complained that the $50 tax, on top of an economic recession, is driving customers away.

Sponsors of the 2006 initiative dismissed the idea that an extra $50 per ticket was significantly affecting the volume of cruise business.

It's just a ludicrous argument that $50 has any bearing on the decision to take a $3,000 cruise vacation, said Chip Thoma, a Juneau activist and founder of an organization called Responsible Cruising in Alaska.

Alaska has attracted about 1 million cruise passengers each summer in recent years. However, some cruise lines earlier this year announced that they are moving ships out of the Alaska trade next summer, likely resulting in a 140,000-person drop in total passengers visiting the state in 2010. Companies have also deeply discounted their Alaska cruises to fill ships, officials have said. (Reporting by Yereth Rosen; Editing by Bill Rigby, Gary Hill)