"I'm Jack," the tape-recorded voice of the man who calls himself "Jack the Ripper" began in the unmistakable Geordie accent of a native of the northeastern coast of England. "I see you are still having no luck catching me.

"I have the greatest respect for you, George," the man, apparently reading a prepared message in a flat, patronizing tone, taunted George Oldfield, assistant chief constable of West Yorkshire. "But, Lord, you are no nearer catching me now than four years ago when I started."

But Oldfield believes that the three-minute cassette recording, broadcast by the media throughout Britain last night and today, may bring him closer to catching a woman-hating psycho-path who has bludgeoned 11 women to death and nearly killed two others in industrial Northern England between October 1975 and this past April.

Patterning himself on the Victorian "Jack the Ripper," who terrorized London's notorious Whitechapel district in the 1880s, murdering and mutilating prostitutes, the "Yorkshire Ripper," as the police and press refer to the killer Oldfield is doggedly pursuing, also preys on prostitutes.

Eight of the women he has killed and one who survived a terrible beating by him were prostitutes, and his other victims were apparently mistaken for them. Most were picked up by the murderer in red light districts of Manchester, Leeds and Bradford. The women have ranged in age from 16 to 42.

"Dirty prostitute bitch," he shouted at a Bradford woman he picked up late last year and hit repeatedly with a heavy metal object, fracturing her skull and opening wounds that required 54 stitches to close. After being left for dead less than 200 yards from the murderer's first victim more than three years before, she gave police their first eye-witness description of the big, handsome although scruffy, long-haired man in his 30s who has become Britain's most prolific murderer in memory.

Promising that he would find another prostitute to kill before the end of the year - "maybe September or October, even sooner if I get the chance" - the killer told Oldfield on the cassett tape, "There's plenty of them knocking about. They never learn, do they, George?"

"At the rate I'm doing," he boasted, "I should be in the Book of Records. I think it's 11 up to now, isn't it? Well, I' keep on going for quite a while yet."

While insisting that the police cannot catch him, he hinted that he would commit suicide if they somehow did close in. Taunting Oldfield right to the end of the tape, he laughingly said he hoped Oldfield would like "the catchy tune" he also recorded on it - four bars from the pop song "Thank You for Being a Friend."

Oldfield, who has said that the massive manhunt for the Yorkshire murderer has become "a personal thing between him and me," is convinced that the recording is genuine. The handwritting on the envelope in which the cassette was sent is the same as that on several letters to Oldfield from the man signing himself "Jack the Ripper." Those letters contained a number of details about the murders that only the killer and the police know.

Voice experts also believe that the tape recording was made by a man from around the North Sea coast town of Sunderland near Newcastle, from where the tape and letters were mailed.

The Yorkshire police "Ripper Squad" believes he either still lives in that area, and frequently travels westward to Yorkshire and Lancashire, where the murders have taken place, or that he frequently returns to Sunderland from a home in the Yorkshire-Lancashire area, where his accent "should stick out like a sore thumb."

For reasons he has not disclosed, but which may have something to do with the murder weapon, Oldfield believes that the man may do some kind of manual engineering work that could involve traveling.

Oldfield, a stocky, balding 55-year-old veteran police officer, has been criticized for not disclosing the nature of the murder weapon or precise kinds of wounds that have marked each crime as that of the same killer. But he believes his Yorkshire detectives are up to the task they have pursued for nearly four years, and that publicizing too much information would both make the killer harder to detect and possibly prompt another demented person to imitate him.

The police were hampered at the beginning, when the first prostitutes were killed, by a lack of information from the public. There seemed to be little concern for the victims, and men who patronized prostitutes were reluctant to come forward.

The investigation picked up when two women survived attacks and talked to the police, and when the two latest victims turned out to have been mistaken for prostitutes. The mother of one of these victims, 16-year-old Jayne McDonald, who had walked through a Leeds red light district on her way home from a discotheque, pleaded for more help for the police.

"How many more must die before people wake up and realize it could happen to someone they love?" Irene McDonald asked in her public appeal in April. "I feel that if (the victims) had all been Sunday school teachers, the public would have come forward with clues and the man would have been found by now."

The response grew enormously today after the cassette recording, which Oldfield received June 18, was played on nationwide radio and television. The "Ripper Squad" has received hundreds of telephone calls that provided new names and leads.

The squad of detectives, augmented at various times by hundreds of police officers throughout Northern England, has already gone through thousands of names of possible suspects, interviewed tens of thousands of people in door-to-door canvases, checked out thousands of cars like those the killer may have driven, and is now finishing a review of employes of hundreds of engineering and construction firms. A $50,000 reward has been offered by the Yorkshire police and a newspaper.

Although the Jack the Ripper of Victorian England was never caught, psychiatrists who have studied the Yorkshire Ripper's letters and tape recording believe he wants eventually to be caught or be killed in the process.

His tape recording also has been played for prostitutes by police in Northern England cities, including those in Manchester, where the killer said he might strike next. Manchester police told prostitutes there they would be safest if they tried another kind of work, but, failing that, they should go out only in twos and threes and note the car license numbers and physical description of their clients.