Radio station WRC-AM said last night that Mort Sahl, controversial and outspoken host of their afternoon radio call-in show, will leave the radio station after next Wednesday.

Sahl asked in late February to be let out of his one-year contract which started Oct. 16, according to Andrew Bergstein, the station's publicity manager.

Bergstein said the station agreed last week to let Sahl go from the job which he said, paid $100,000 annually.

"His movie and television career are just skyrocketing," said Frank Scott, Vice president and general manager of WRC. "It was getting difficult for him to just be here."

Sahl's contract had allowed him a leave of absence to direct a film script which he wrote called "Marina del Ray." But last moth, Bergstein said, he contracted to write pilots for two possible situation comedy pilots and he was cast for a supporting role in a film called "How the West Was Shrunk," to be filmed in Canada. Sahl could not be reached for comment last night.

"We were extremely reluctant to let him out of his contract," said Bergstein, "but you realize when someone's a hot property they can be stolen."

Sahl, long a political satirist and one-time darling of the late '50s and early '60s liberals, had taken to attacking some of those liberals in recent years. "He attacks whoever is on top." explained Bergstein, who says he has come to be close friends with Sahl since he came to Washington.

He incensed women's groups and homosexuals as well as a variety of others in the area. During his hours on the air, Bergstein said, the switch-board floods with calls from people wanting both to talk to him and to complain about him.

Asked if Sahl was fired, Frank Scott said, "Oh, no, not at all. I plan to go on the air tomorrow [at the beginning of his show] and announce that he's leaving and say we regret it. He's done a sensational job."

Over the first two months that he was at the station, the ratings for the station during that 4-to-7 afternoon "drive-time" slot doubled, Bergstein said. More recent ratings will be out within the next two weeks, he said.

The afternoon slot will be filled by political columnist Tom Braden and former Nixon speechwriter Pat Buchanan who now host a morning call-in show called "Confrontation," a debate between liberal and conservative political views.

WRC-AM had planned to announce Sahl's departure today, but a station official slipped and let the secret out. A listener called in yesterday to complain about Sahl, and the station official, in what Bergstein called a "mental lapse," told the listener, according to Bergstein, "Sahl's only gonna be on the air another week, so don't worry."

The listener promptly called Sahl on the air and told him what had happened. Sahl, surprised, tried to hedge the issue. None of his later callers mentioned it on the air.