Duke Energy CEO Jim Rogers, in a contrite letter to the N.C. Utilities Commission, says Duke’s public criticism of the commission over its investigation of the Duke-Progress Energy merger was inappropriate.

The letter, filed Tuesday, was required under a settlement agreement ending the probe that the commission verbally approved last week.

It repeats the agreement’s wording that Duke doesn’t admit illegal or improper acts but acknowledges “that our activities on this matter have fallen short of the Commission’s understanding of Duke Energy’s obligations” as a regulated utility.

“Duke Energy is a company that can be trusted,” Rogers wrote.

In an apparent effort to mend relations with Duke’s most important state regulators, Rogers also apologized for public criticisms of the commission by Duke.

“I wish we could retract the statements made regarding the manner in which the hearings were conducted and regarding the Commission’s actions,” he wrote. “We cannot undo what was said, but we acknowledge that our public criticism of the Commission was inappropriate.”

Duke called July hearings at which the commission heard from former Progress CEO Bill Johnson and two former Progress directors one-sided. Commission chairman Edward Finley denied Duke’s request for its lawyers to cross-examine the witnesses.

“The only party affected (Duke) was not allowed to participate in the hearing,” Raleigh lawyer Burley Mitchell, a former N.C. Supreme Court chief justice who represented Duke, later told reporters. “I’m very disappointed that we were just cut off.”

In a separate filing, the Utilities Commission said it won’t reconsider its June 29 approval of the merger, ruling against a persistent Duke critic, the Durham-based advocacy group N.C. WARN.

WARN has claimed that Duke withheld information on key issues that could affect the merger’s costs to North Carolina consumers.

Those costs related to the repair or retirement of the crippled Crystal River nuclear plant in Florida and $2 billion Duke expects to spend to upgrade other former Progress-owned nuclear plants. WARN also claims Duke didn’t signal its growing loss of confidence in former Johnson, who was later fired, before the merger closed.

The commission ruling, signed Monday, called the Crystal River claim “completely without merit,” saying North Carolina customers won’t be asked to pay costs of a Florida plant.

It said customers of Progress Energy Carolinas, now a Duke subsidiary, would pay any costs of other former Progress nuclear plants that Duke tries to recover through rates.

The commission said WARN’s claims that settlement agreements between Duke, consumer advocates and other parties will increase merger costs and be passed to customers have “no merit.”

The panel said claims about Duke’s pre-merger discomfort with Johnson should be directed to the commission’s separate investigation probing his dismissal. The commission orally voted last week to accept settlement agreements resolving that investigation, but has not yet filed a written order.

WARN has said it would appeal the merger settlement in court.