INDIANAPOLIS—Health insurance giant Anthem is strongly criticizing the U.S. Department of Justice (DOJ) for attempting to block Anthem’s proposed acquisition of rival insurer, Cigna.

Last week, the DOJ and attorneys general from multiple states and the District of Columbia filed a lawsuit seeking to prevent the mega-merger, as well as a similar deal involving Aetna’s proposed acquisition of Humana. The suit alleged that the transactions would increase concentration and harm competition across the country, reducing from five to three the number of large, national health insurers in the nation.

In a statement issued Friday, Anthem called the DOJ suit “an unfortunate and misguided step backward for access to affordable health care for America.” Anthem said, “Access to health insurance saves lives, improves health and reduces the cost of care for all Americans. The DOJ’s action is based on a flawed analysis and misunderstanding of the dynamic, competitive and highly regulated health care landscape and is inconsistent with the way that the DOJ has reviewed past health care transactions.

“Anthem has an unwavering commitment to enhancing access to affordable health care and the benefits and efficiencies from its merger with Cigna is one way that Anthem will continue its mission of improving consumer choice, quality and affordability. Anthem is fully committed to challenging the DOJ’s decision in court but will remain receptive to any efforts to reach a settlement with the DOJ that will allow us to complete the transaction and deliver its benefits at a critical time when American consumers are seeking high quality health care services with greater value at less cost,” according to the Anthem statement.