Former president Jimmy Carter criticized The Washington Post yesterday for failing to apologize for a gossip item asserting that there were rumors Blair House had been bugged during his administration.

"It's clear The Washington Post has decided not to retract its original story and not apologize for it," Carter told reporters at National Airport as he prepared to fly to Pennsylvania for a fishing trip.

He added that he will decide "within a few days" whether to sue the paper for libel. "This matter is certainly not closed," he said, noting, "This is a very serious allegation against me and/or Rosalynn, that we did indeed bug the conversations of President-elect Reagan and his wife."

In an editorial on the flap in yesterday's editions, The Post noted that the paper's "Ear" gossip column had reported 10 days ago that there was a "rumor around" to the effect that the Carters had bugged Blair House.

The editorial asserted that such rumors were, indeed, floating around, but then added: "Based on everything we know of the Carter instinct and record on this subject, we find the rumor utterly impossible to believe."

Carter, who last week had a lawyer write the paper demanding a retraction and an apology, said yesterday he did not consider the editorial an adequate resolution of the matter. "The editorial simply confirms the story was false, it was slanderous in its effect and they knew it to be false in the beginning before it was published," he said.

Former presidential press secretary Jody Powell said he was angered and disappointed by the editorial. "The Post is taking the position that there was nothing wrong with printing a rumor it believed to be false . . . . Now there may be some legal technicality that allows them to do that, but the president doesn't think so.

"I really thought that in the end, the paper would just come out and say, look, we made a mistake and we're sorry," Powell continued.

Post Publisher Donald E. Graham declined to respond to the criticism. "The editorial speaks for itself," he said.