JACKSON — Another credit rating agency has downgraded its view of Mississippi Power Co.

Two of the three major agencies have now cut ratings after the Mississippi Public Service Commission denied Mississippi Power a rate increase to pay off debt during construction of its $2.8 billion Kemper County power plant.

Moody’s Investors Service cut its rating on about $1 billion in company debt by a notch last week. It now rates Mississippi Power as A3, still an investment grade. Moody’s also said it had a negative outlook for the future, meaning it could cut grades again.

Fitch Ratings announced a downgrade in July.

Moody’s cited the debt the Southern Co. subsidiary has incurred in building Kemper, as well as the failure to win the $55 million rate increase from the PSC.