It's a case of another state, another anti-trust lawsuit for Marsh & McLennan. Connecticut Attorney-General Richard Blumenthal has filed an action in the State Superior Court against Marsh reinsurance brokerage unit Guy Carpenter.

Like his counterparts in Ohio and New York State, Mr Blumenthal says the company acted as a ringleader in a price-fixing cartel of reinsurers. He alleges it created a nationwide reinsurance market that was insulated from competition.

"Thousands of consumers in Connecticut and many more in most states across the country paid premiums up to 40% higher, costing them potentially hundreds of millions of dollars.

"We are drawing back the cloak of secrecy on industry practices that inflated prices and profits at the expense of 170 insurance companies and their customers."

Guy Carpenter says it will vigorously defend the lawsuit - there is no legal basis for it and the unit is confident in its defence.

"The complaint is based on a fundamental misunderstanding of reinsurance facilities that have been in operation for as long as 50 years.

"These facilities result in improved availability and terms of reinsurance and ultimately benefit insurance buyers."

But Mr Blumenthal is equally confident. He says the European Commission on Competition has already found the practices to be anti-competitive.

Marsh & McLennan has already paid $US850 million ($941 million) in fines and damages to New York State, after a 2005 investigation by its then Attorney-General (and now Governor) Eliot Spitzer. It is also defending an anti-trust lawsuit filed by the State of Ohio.