Organized crime, transformed by new ethnic groups and criminal gangs, is cheating the nation of more than $18 billion a year and costing it more than 400,000 jobs, the President's Commission on Organized Crime concluded yesterday.

In a final report, the commission warned that "we must broaden our perspective" beyond the traditional preoccupation with the Mafia and realize that the problem has become much more pervasive.

Half of the commission members, however, complained about the quality of the panel's work, chastising it for failing to assess the federal government's anticrime efforts and leaving other important issues unexplored.

Appointed by President Reagan in 1983, the commission found that at least four outlaw motorcycle gangs had evolved "into full organized crime groups" with chapters reaching into Europe and Australia.

More recently, the report said, self-perpetuating gangs have established themselves in U.S. prisons, with at least five groups -- the Mexican Mafia, La Nuestra Familia, the Aryan Brotherhood, the Black Guerrilla Family and the Texas Syndicate -- apparently meeting "the criteria of an organized crime group."

"All five operate in more than one state," the panel said. "In all five, either murder or the drawing of blood are prerequisites for membership."

Beyond that, the commission said, secret Chinese criminal societies known as Triads, Vietnamese gangs preying on fellow immigrants, Japanese "Yakuza" groups, Cuban crime cartels, Colombian cocaine rings, holdover Irish gangs and even newly established Russian organized-crime groups are flourishing in different areas of the country.

"There will be little lasting benefit in disabling La Cosa Nostra if other groups successfully claim its abandoned criminal franchises," the commission said. "Several groups are obviously able and eager to do so."

The 222-page report, entitled "The Impact: Organized Crime Today," includes a number of supplemental and dissenting views that reflect deep dissatisfaction within the 18-member panel, especially over the performance of its staff and of the chairman, U.S. Circuit Court Judge Irving Kaufman.

One supplement, signed by nine commissioners, complains that "poor management of time, money and staff has resulted in the Commission's leaving important issues unexamined," especially questions about the effectiveness of federal and state efforts against organized crime.

"The true history of the . . . Commission is a saga of missed opportunity," the nine panelists said. They said the group had done "some good work," but was hampered by unrealistic deadlines, resistance to meetings to review draft reports, and at times "final drafts which were not even shown to commission members before publication."

Yesterday's report was shown to them and was much thinner as a result, sources said. "We junked a lot of stuff -- whole chapters in instances," said one member, who asked not to be named. "There was no split over issues, it was all over quality . . . It [the group] was too unwieldy."

In a telephone interview, executive director James Harmon emphasized the commission's study on "The Income of Organized Crime," conducted by Wharton Econometric Forecasting Associates Inc. of Philadelphia and released yesterday as part of the final report.

The study estimates that organized crime reduces the Gross National Product by $18.2 billion a year, reduces U.S. employment by 414,000, raises consumer prices about 0.3 percent and makes a $77.22 dent in per capita personal income.

"It distorts market forces and makes the legitimate economy operate in a less efficient way," Harmon said.

The Wharton study also estimates that 1986 net income from organized crime activities would be in a middle range of $46.6 billion and implied gross receipts would come to $65.7 billion.

If most of that makes its way into the economy, it would suggest that organized crime is a net contributor to the GNP, but commission spokesman Art Brill said he could not comment on that possibility.

The Wharton study acknowledges flaws in methodology, including the fact that the commission's own survey of law enforcement agencies resulted in some double-counting of the underworld population. One source said the commission asked New Jersey state authorities and police officials in Newark and Camden how many Mafia members were in their jurisdictions, then tallied them all.

About new ethnic inroads into organized crime, the panel said that first indications of a Russian element came in 1975, and by now there are about "12 Russian organized crime groups in New York, with a total strength of 400 to 500 members."

As for prison gangs, the Justice Department has identified 114, including such groups as the Mexican Mafia, which began in 1957 with members of youth gangs incarcerated at Tracy, Calif., and the Aryan Brotherhood, a white Nazi-oriented gang that started at San Quentin and now has branches throughout the federal prison system.

The nine commission members who complained of "serious shortcomings" in the report praised the effort to shed light on "some heretofore ignored" crime groups, but complained of the failure "to address the role of American black and Jewish organizations" in organized crime.