NEW YORK (Bloomberg) — OneBeacon Insurance Group, the Bermuda insurer with offices in 11 US states, was sued by rival Beacon Mutual Insurance over claims it defied a court order to stop using its name and logo in Rhode Island.

Beacon Mutual, based in Warwick, Rhode Island, sued OneBeacon for trademark infringement in 2001, claiming the companies' similar names and lighthouse-themed logos were confusing to existing and potential customers.

Although OneBeacon lost the case in July 2005, it's violating a court order by continuing to use the name and logo on envelopes, Web site addresses and various customer communications in Rhode Island, according to the civil-contempt suit filed December 6 in federal court in Providence.

"The court recognized the validity of our arguments in 2005," Beacon Mutual spokesman Bill Fischer said yesterday in an interview. "We're going back to the courts to ensure OneBeacon complies 100 percent with the court order."

Beacon Mutual, which is seeking unspecified damages, court costs and attorneys' fees, claims it has used various "Beacon" trademarks with a lighthouse logo since 1992. OneBeacon began using the name and lighthouse logo in 2001 after changing its name from CGU, according to the suit.

"If defendant does not cease use of the OneBeacon name" in Rhode Island, "confusion about the distinction between the parties' insurance products and services will be perpetuated," Beacon Mutual said in the complaint.

OneBeacon, whose US headquarters is in Canton, Massachusetts, raised $600 million in an initial public stock offering in November 2006. The property and casualty insurer had been the largest unit of White Mountains Insurance Group, which bought OneBeacon in 2001 from Aviva, the UK's largest insurer.

OneBeacon spokeswoman Carmen Duarte declined to comment on the litigation.

OneBeacon fell 36 cents to $21.05 in New York Stock Exchange composite trading.