If the latest official report of the House Assassinations Committee could be labeled neatly, "Twice Told Tales" might do.

In preparation for last week's showdown vote continuing the congressional inquiry into the murders of President Kennedy and the Rev. Martin Luther King Jr., the besieged 12-member committee decided to offer a public preview of its investigations thus far.

Most of the material in the 14-page status report was uncorroborated and had a vaguely familiar ring.

The report raises serious questions about both the accuracy of the committee's work and its inclination to present twice-told tales as though they were fresh leads too sensitive to disclose with any particularity.

After announcing that the 67-member staff is assiduously pursuing "new leads" in the Kennedy assassination, for instance, the report confides:

"Recently, an FBI informatn advised the Committee that he had seen an FBI agent and Lee Harvey Oswald meeting together on numerous occasions in various New Orleans bars. The informant states that he had previously denied seeing Oswald and the agent together because he was threatened by the agent. The agent has denied the informant's charge."

In this case, the committee appears to be just getting around to what millions of Americans saw and heard on Nov. 26, 1975, on a CBS-TV program entitled "The American Assassins."

While the cameras rolled, New Orleans bar operator Orest Pena openly asserted, and FBI Agent Warren DeBrueys openly denied, that DeBrueys and Oswald often met in the city's French Quarter, especially at a Greek restaurant.

Pena's story had changed quite a bit from his Warren Commission testimony that he had seen Oswald in the company of a Latin-looking man in August of 1963 at Pena's own Habana Bar and Lounge, where Oswald distinguished himself first by ordering lemonade and later by getting sick.

Pena's CBS appearance is dismissed with a vulgarity by Harold Weisberg, who has written a series of books on the Kennedy and King assassinations and who has become an outspoken critic of the House inquiry.

"Orest's an old friend of mine," Weisberg adds. "Everybody keeps asking him crazy questions leading to a whole set of confabulations. But I don't think he thinks he's making anything up. He's just lost in all of this. God knows who's been telling him what."

Item - According to the House report, "a witness who was in an FBI security code clerk in the New Orleans office from 1961-'66 alleges that the FBI sent a teletype to all of its offices five days before the assassination, warning of a reported conspiracy to assassinate President Kennedy on his proposed trip to Dallas on November 22-23 (1963) . . . The FBI has denied sending such a teletype."

This story originally popped to public attention on another television program back in 1968 featuring Jim Garrison, then the district attorney of New Orleans. According to an Oct. 21, 1975, hearing before the House Subcommittee on Constitutional Rights, moreover, the code clerk, William Walter, had not only added new twists to the story over the years, but also did poorly on a polygraph test provided under the auspices of the Dallas Times Herald in 1975 when the story surfaced again. (In the words of an FBI official, "there were indications of deception on the part of Mr. Walter" but "the results were inconclusive because of the limited number of questions . . . ")

Item - The committee is "intensively" investigating an alleged conspiracy against King stemming "from a report by a now-deceased undercove r informant of a southern police department. Immediately prior to Dr. King's death," the report states, "he told his superiors that he had recently overheard a conversation between members of two organizations in which it was said that when Dr. King returned to Memphis they would be forced to kill him."

The fact is that the informant, the late Willie Somersett, did not tell his superiors (Miami police and Dade County prosecuting authorities) about the purported conversation until nearly three weeks after King was killed.

Somersett did voice vague apprehensions about King before the murder to Miami Police Lt. Charles Sapp, as readers of last October's issue of Miami Magazine have known for months. But Somersett's "control" officer, former prosecutor Seymour Gelber, now a Dade County Circuit Court judge, told The Washington Post in a telephone interview that he has strong reservations about Somersett's report because "the story was not given to us until after King's death. I think that makes it a lot different."

Item - Solemnly stating that its investigation has "uncovered other areas of possible assistance" to James Earl Ray (now serving a 99-year prison term for King's murder), the committee declares: "According to bank records, Ray's safety deposit box in Birmingham was closed by someone living in Baton Rouge. At the time of the closing, however, Ray was living in Los Angeles."

Weisberg, who has done investigative work for Ray and spoken with him, charges that "what they say here is false.

"The bank deposit box was closed by a letter from Ray postmarked Baton Rouge. The bank close the box and threw the letter away. I think he wrote the letter in Los Angeles and mailed it in Baton Rouge on his way to New Orleans."

None of this should be taken to mean that there are not many questions to be answered if the House inquiry is to be conducted. But as George McMilan, author of book about Ray called 'The Making of an Assassin," puts it:

"I really don't think they should take things that have been cleared up and talk about them so provocatively when they should know better."

The itemization is far from complete. In one especially questionable sentence, the committee has an FBI ballistics expert testifying at Ray's guilty plea hearing (he didn't) about whether the fatal bullet (he said in an affidavit it was too distorted) came from the rifle "allegedly" purchased by Ray.

Declares James Lesar, Ray's erstwhile attorney who says he still represents him: "Of all the things that are not in dispute, it is that Ray purchased the rifle . . . They don't know the facts [of either assassination] yet. So they're not even in a position to judge the credibility of the people who come to them."

In still another dubious excursion, the committee has now labeled a man who not long ago emerged from a psychiatric ward, George de Mohrenschildt, as a "crucial witness" although he had just committed suicide. Neither the Assassinations Committee nor its staff ever interviewed the man, a White Russian who had befriended the Oswalds in Texas in 1962.

In fact, House investigators possess little more than a Dutch television film tape and one tape cassette "allegedly" containing a conversation between de Mohrenschildt and Dutch journalist Willem Oltmans.

In a spate of interviews since de Mohrenschildt's death Tuesday afternoon, Oltmans has been quoting him

In a spate of interviews since de tween Texas oilmen and Oswald in a baroque kill-Kennedy conspiracy, which also seems to have included anti-Castro Cubans and a trucking firm executive.

Curiously, by Oltmans' account, de Mohrenschildt did not come up with the story until February - more than 13 years after the assassination but only a few weeks after his release Dec. 30 from the psychiatric unit of Parkland Memorial Hospital. And although Oltmans quoted de Mohrenschildt as saying Oswald took instructions from him, that is somewhat difficult to square with the fact that the de Mohrenschildts were in Haiti at the time of the Kennedy assassination and had been there for about five months. They told the Warren Commission they last saw the Oswalds in April of 1963 and, the commission found, "they never saw either of the Oswalds again."

Charges Weisberg: "There's not one thing they've come up with that has established relevance. They've been in business six months, they've had a staff of 73 people, and they can't even read accurately from other people's work. I have never seen a more total confession of bankruptcy."

However that may be, the committee is clearly following the "scenario" laid out at a secret March 17 meeting when its since-resigned March 17 meeting when its since-resigned chief counsel, Richard A. Sprague, warned the members that the potentially significant items compiled thus far were much "too raw and uncorroborated for us to be stating publicly."

Rep. Samuel L. Devine (R-Ohio) responded but suggesting that the committee might take some of the "literally hundreds of undeveloped leads" on hand and make them public in bowdlerized fashion.

That way, Devine suggested, the committee could 'let people know that, 'My God, they are onto something that is new stuff . . ."

According to one well-placed source, with Sprague gone the pressures to find a conspiracy are bound to increase. This source says Sprague, as an investigator, was actually "a moderating influence."