The Carnival Triumph cruise ship is towed towards the dock as spectators watch at the port of Mobile, Alabama on February 14, 2013 (© Lyle Ratliff-Newscom-Reuters)
Carnival (CCL), the world's largest cruise operator, has rejected a request from a powerful U.S. senator that it reimburse the U.S. government for the costs it incurs for rescuing the company's ships when they become disabled.

According to Senator Jay Rockefeller, D-W.Va., the U.S. Coast Guard has responded to 90 "serious events" involving Carnival ships over the past five years, including the rescue of the Carnival Triumph (pictured) in February and the 2010 operation to assist the Carnival Splendor. The Coast Guard and Navy spent $4.2  million to assist the Triumph and Splendor, which were both hit with power failures, according to a report in quoting Rockefeller.

The Triumph made more news Wednesday after it broke loose from its repair dock during a storm. Sadly, a security guard was knocked into the Mobile River and hasn't been seen since, according to CNN.

In a letter to Carnival, Rockefeller noted that the company should repay the government for its help because the Panama-based operator pays "little or nothing in federal taxes." Carnival rejected Rockefeller's request, arguing its policy is to "honor maritime tradition" to render assistance to those at sea in need of assistance.

Carnival noted that it provides assistance to the Coast Guard when asked. The company also argued that it pays its fair share of fees to local, state and federal agencies.

Rockefeller, the chairman of the Senate's Commerce, Science and Transportation Committee, wasn't satisfied.

"Carnival's response to my detailed inquiry is shameful," he said in a statement to MSN Money. "I am considering all options to hold the industry to higher passenger safety standards."

Officials at Carnival couldn't immediately be reached.

Jonathan Berr does not own shares of the listed stocks. Follow him on Twitter @jdberr.

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