A false report that D.C. Mayor Marion Barry had been shot last night was broadcast on three television channels and swept quickly through the city by word of mouth, creating an hour of confusion before it was authoritatively denied.

The report apparently stemmed from a telephone call to at least one television station by a man who indicated that he was speaking from the city's emergency command center and said the mayor had been wounded.

Confusion escalated after the report was broadcast about 9:50 p.m. on WRC-TV, Channel 4, and then repeated on two other channels. The story spewed from United Press International printers and spread through the streets and from house to house by telephone. Hospital emergency room personnel were alerted. Calls flooded into authorities here from as far away as Australia.

Finally, the mayor appeared on the steps of his house in Southeast about 10:45 p.m. to assure reporters and about 70 citizens gathered there that he was unscathed and the rumors were false.

The mayor had been at a reception early last night and was at the home of his lawyer, Herbert Reid, about 10 p.m. when he heard a televised report that he had been shot. The news was delivered by WJLA (Channel 7) anchorwoman Renee Poussaint.

As the mayor later recounted it, "I looked at her and said, 'What the hell's going on.'"

The mayor telephoned his command center and also called a top aide to say he was unhurt, but for a frantic hour last night few people in Washington, whether public officials or private citizens, appeared to know what was happening. City leaders said they would investigate the hoax, and an FBI spokesman said an effort would be made to learn whether any violation of federal laws was involved in the incident.

Anxious minutes passed while the false report outsped the attempts of exasperated officials to deny it. Members of the city council said they knew only what they heard on radio or television. Those members who could be reached last night said they first learned of the report from news broadcasts or from relatives or constituents who called them. They emphasized that no one in any official capacity confirmed the reports.

Councilwoman Wilhelmina Rolark (D-Ward 8) said her daughter telephoned her to say that she had heard on the radio that the mayor was in critical condition.

Councilwoman Betty Ann Kane (D-At Large) said she tried to call the mayor's command center, but received only a busy signal.

The inability of callers to reach the mayor at home also apparently fueled the rumor. The confusion may have been heightened by an accidental shooting of an off-duty police officer, which occurred around the corner from the mayor's house about an hour before the false report began.

By late last night the source of the confusion had been traced to a telephone call reportedly made to the NBC national news bureau here by a man who identified himself as James Taylor and said the mayor had been shot.

The bureau shares quarters here with WRC, the local NBC outlet. According to WRC spokeswoman Barbara Holtzberg, the caller left a telephone number at which he said more information could be obtained.

Holtzberg sid the report was passed to Channel 4 anchorman Marty Levin and that someone working for him called the number. The call was answered by a person who said: "Mayor's command post," and then "confirmed" that the mayor had been shot, Holtberg said.

Officials at the command center said later that nobody there told any caller that the mayor had been shot.

Indications emerged later that the telephone number may have been that of a pay telephone in the 600 block of Pennsylvania Avenue NW.

Interrupting regularly scheduled programming, WRC reported about 9:50 p.m. that the mayor had been shot and was being flowny by helicopter to the hospital at Andrews Air Force Base.

When WDVM, Channel 9, learned of the WRC report, the station telephoned Andrews. An assignment editor at WDVM said the station called a base command post and received information from a "Sgt. McLaurin" that the mayor had indeed been shot and that the base hospital had been asked to prepare the emergency room.

However, Col. Bob Thatcher, a public affairs officer at Andrews, said no one named Sgt. McLaurin is assigned to the base. Thatcher said a switchboard operator at the command post told a caller that he had heard on television that the mayor had been shot and was on his way to the base.

Thatcher said the hospital prepared its emergency room, apparently in response to a television broadcast, "as we would if we received any word that there was an emergency and that Andrews was involved."

WJLA said they never received any call from the man purporting to be James Taylor. "I guess he didn't like us," said News Director Dallas Smith, who said his station learned about the story when it was broadcast on Channel 4.

WDVM broadcast the story at 10:02 p.m., according to night assignment editor Ellen Dahut. About the same time, WJLA also broadcast the report, which was viewed by the mayor.

At 10:03 p.m., the rumor was given added impetus when United Press International reported that according to WDVM-TV, the mayor had been shot and was in critical condition at Andrews.

By 10:12 p.m., WDVM was back on the air saying the report was false.

About the same time, according to Dahut, a man identifying himself as James Taylor called her and said the mayor had been shot on his front lawn, had been flown to Andrews by helicopter and was dead.

He gave a telephone number that the station tried to call. It was busy.

After hearing the report on television, however, Barry called command center personnel to tell them it was untrue. Gradually, between 10 and 11 p.m., denials began overwhelming the rumor.

City administrator Elijah Rogers held a press conference outside police headquarters to tell about a dozen reporters that no shooting had occurred. "The mayor is safe," Rogers said. "That's the story."

"It's not true," police homicide Lt. Carl Alexander told reporters even before they could beging asking about the reported shooting.

Finally, the mayor arrived home and denied the rumor a final time.

After spending five minutes in the house, he emerged to the cheers of a milling crowd to say: "I was as surprised as anyone else."

With his wife on his arm, the mayor expressed his appreciation for the public's concern and called the hoax "a horrible way to play a joke."

"This is one of the worst tricks anyone can play," said the mayor's wife, Effi, who heard the rumor while visiting a friend in Southwest. "I'm just numb."