The increases would have taken effect April 1 for plans covering thousands of small businesses and individuals.
The insurers are scheduled to go before a judge in state Superior Court Thursday seeking a preliminary injunction against last week's rulings by Insurance Commissioner Joseph G. Murphy to reject 235 of 274 premium hikes proposed by the health insurers.
Those rulings, following emergency regulations set by Governor Deval Patrick, marked the first time the state has used its authority to deny premium increases.
"What the commissioner did, we think, is going to create tremendous disruption in the marketplace," said Dean Richlin, a partner at Boston law firm Foley Hoag, who is representing the insurers.
Jason Lefferts, a spokesman for the insurance commissioner, this afternoon said his office had just learned of the lawsuit and had no immediate response.
Filing the suit were Blue Cross Blue Shield of Massachusetts, the state's largest health insurer, as well as five members of the Massachusetts Association of Health Plans: Harvard Pilgrim Health Care, Tufts Health Plan, Fallon Community Health Plan, Health New England, and Neighborhood Health Plan.
All are non-profit carriers. The complaint, filed about 2 p.m., alleges that the state Division of Insurance acted illegally in three ways: by imposing a rate cap it had no authority to impose, by pegging the rate cap to a measure - the medical consumer price index - that has no actuarial significance, and by violating a statutory requirement to enable insurers to charge adequate rates based on the projected utilization of medical care.
"As a result of the commissioner's action," Richlin said, "the insurance companies will experience substantial and, in some cases, staggering losses. We estimate the collective loss among all of the insurers will run into the hundreds of millions of dollars just for 2010. There are some number that will face near-term solvency problems."