FairPoint Communications on Thursday declared an impasse after four months of contract talks with two unions and imposed its final offer that freezes the current pension plan and eliminates retiree health care benefits. The unions accused the company of refusing to bargain in good faith.

The telecommunications company announcement came a day after unions representing more than 1,700 workers in Maine, New Hampshire and Vermont delivered a comprehensive contract proposal, which they said aimed to reduce the company’s operating costs.

The unions responded to the company’s claim of an impasse by filing a complaint with the National Labor Relations Board, accusing FairPoint of violating federal law by refusing to bargain in good faith.

“We have not reached impasse. The company should stay at the table and continue to work with us to reach an acceptable agreement,” said Peter McLaughlin, chairman of the unions’ bargaining committee and business manager of International Brotherhood of Electrical Workers Local 2327 in Augusta.

Union workers already authorized a strike but had been working under terms of a contract that expired Aug. 2.

The contract talks had started in April. Effective Thursday morning, FairPoint imposed its final offer, which it says is permitted under federal law. “It is regrettable that the issues could not be resolved through bargaining,” company spokeswoman Angelynne Amores Beaudry said in a statement.

The final proposal now in effect keeps wages unchanged, but it addresses some if the company’s key concerns: pension liability and health care costs.

Under the new plan, the company is freezing the existing defined benefit pension plan, while preserving employees’ current accrued benefits and implementing a new plan. The company also eliminated retiree health care benefits for current employees, and it also required current employees to share some health care costs for the first time.

The International Brotherhood of Electrical Workers and Communications Workers of America said the company never put forth a counter offer to any of the unions’ proposals.

“The company has refused to bargain with us, and their negotiators have even attempted to intimidate and bully us throughout the process,” said Glenn Brackett from IBEW Local 2320 in Manchester, New Hampshire.

North Carolina-based FairPoint has contended its old contract that retained virtually all of the benefits that workers had enjoyed under Verizon were out of sync with industry norms.

FairPoint grew six-fold overnight when it bought Verizon’s land holdings in northern New England for $2.3 billion in 2007. The company lost customers as it struggled because of operational and integration problems, and the company filed for Chapter 11 bankruptcy about 18 months later.

FairPoint has continued to struggle since emerging from bankruptcy in 2011. The company has yet to reverse net losses posted for every year of operation since the Verizon purchase.