The number of inmates in state and federal prisons climbed to nearly a million last year, an almost threefold increase since 1980, according to a Justice Department report issued yesterday.

Last year's growth alone represented an average weekly gain of about 1,250 prisoners. Congress is poised to stiffen penalties for dozens of crimes, thereby exacerbating the problem. The Bureau of Justice Statistics said that nearly half the increase in prisoners since 1980 was linked to drug offenders entering prison. In 1992, the last year for which data on drug offenders were available, prison commitments for drug offenses reached 30 percent of all new commitments, the department said.

The "War on Drugs" produced longer federal and state sentences, mandatory minimum terms and tighter parole policies for drug and violent crimes.

In addition to drug offenders, the numbers of people jailed for sexual assault, robbery, aggravated assault and burglary have increased, the report said. Those crimes accounted for nearly 50,000 people entering prison in 1992, according to the Justice Department.

Inmate growth also was linked to increases in the number of parole and probation violators returned to prison. In 1980, only 17 percent of state prisoners were parole or probation violators, but by 1992 this had risen to 30 percent.

Overall, the nation's prisons held 948,881 inmates at the end of last year, compared with 329,821 men and women in 1980. The average annual increase for the 14-year period was 8.5 percent.

At the end of last year, state prisons were estimated to be operating at between 18 and 29 percent above capacity, while the federal system was estimated to be 36 percent over capacity.

The rapid rise in incarcerations underscored the fiscal impact of rising crime rates, primarily on state governments. Corrections officials estimate that it costs at least $15,000 a year to house each prisoner, and say the cost of building prisons has been rising annually. "In recent years, the increase in correctional spending for states has been twice that for general fund increases and even larger than in education spending," said Jon Felde, who studies judiciary issues for the National Conference of State Legislatures.

"We have to find new ways to cope with the rate of criminality," he added. Felde predicted that state governments would intensify their searches for sentencing alternatives to incarceration. Joseph R. Biden Jr. (D-Del.), chairman of the Senate Judiciary Committee, said that the Justice Department report makes all the more imperative the need for Congress to pass the crime bill, which authorizes billions of dollars for prison construction besides lengthening sentences for a number of crimes.

"But it is not enough simply to keep building prisons because -- as the statistics released demonstrate -- the prison population keeps growing to fill new spaces," he said.

Biden called for a "new approach" to fighting crime, balancing punishment with innovative prevention programs and expanding cost-effective experiments such as boot camps and special drug courts.

The report said that California had the most inmates in state facilities in 1992 (119,951), followed by Texas (71,103) and New York (64,569). Texas had an additional 29,546 inmates in local jails awaiting transfer to state prisons. The report stressed -- and law enforcement officials confirmed -- that inmate overcrowding and rising costs of incarceration have forced a number of states to begin housing prisoners in local jails. At the end of last year, the report said, 22 states reported a total of 50,966 such prisoners being held in local jails or other facilities.

Texas reported that almost 60 percent of its prisoners were being held in local jails even though they had been sentenced to state prisons, and four other states -- Louisiana, Virginia, New Jersey and West Virginia -- held more than 10 percent of their prison populations locally, the report said.

Bud Meeks, executive director of the National Sheriff's Association, said, "Incarcerating people is a very expensive proposition for us. We feel the increase because our local jails are turning into long-term facilities, which they really are not equipped to be."

Meeks said one local jail in Fort Wayne, Ind., was housing 540 inmates, even though it was built for 220. "That's happening all over... . It's a disaster waiting to happen," Meeks said.