When Willie Parker began driving trucks for the government nearly 11 years ago, his job at the Naval Research Laboratory here included short hauls around the Washington area and longer, overnight journeys to military and supply centers in Ohio, Pennsylvania and the Tidewater area of Virginia.

The longer trips have since been contracted out to private trucking firms, and these days Parker says he and 31 other Navy drivers aren't allowed to travel more than 50 miles from the District-based facility.

Now Parker and his colleagues are deeply worried that the next step will be elimination of all their jobs by contracting out -- a trend that is firmly established throughout the government and being further encouraged as a budget-cutting device by the Office of Management and Budget.

The motor pool workers already have heard the whisper of the budget ax -- it descended on most of the custodial workers at the laboratory when their jobs were contracted out about three years ago.

OMB officials have ordered a review, now being conducted by all government agencies, military and civilian, to determine if more federal jobs should be contracted out. The Naval laboratory, where 128 positions are under review, the Washington Navy Yard, the Veterans Administration and the General Services Administration are just some of the local facilities where workers fear their jobs may be targeted for elimination next.

"I thought a job with the government meant security, but right now we all feel pretty terrible," said Parker, a 42-year-old father of three who lives in Capitol Heights, Md. As a Wage Grade-11 employe, he earns about $21,000 a year.

Workers such as Parker are the government's blue-collar forces, its drivers, mechanics, groundskeepers, janitors, laundry, food services and other trade or craft employes. But since the late 1950s, their once-populous ranks have been declining steadily as more and more of these federal tasks and services are contracted out.

Two decades ago, there were more than 663,000 blue-collar workers nationwide, 40,000-plus of them in the Washington area. Today, about 488,000 of the federal government's total 2.1 million work force, excluding the U.S. Postal Service, are blue-collar workers, and only 32,150 of them, a nearly 21 percent decline, work in the Washington region.

Andy Spisak, a government statistician with the Office of Personnel Management, notes that the number of federal blue-collar workers has fallen off while the number of white-collar workers has risen more than 300,000 nationally in a roughly comparable period. Further, the declines have hit minority workers the hardest, since blacks and Hispanics make up nearly 30 percent of the blue-collar work force and account for more than 53 percent of the government's manual laborers.

Federal officials say there are a number of reasons for the decline in blue-collar jobs. Some have been reclassified or phased out as the government has become more technically oriented. Elevator operators, for example, are a dying breed now that most facilities have automated lifts. But most of the job losses are the result of contracting out work once done by federal employes.

In contracting out, officials at federal agencies say, they save millions of dollars in payroll costs by trimming the personnel rosters and eliminating the need to pay for expensive pension and health benefits.

At the Department of Defense, which accounts for about 63 percent of all federal blue-collar workers, nearly 8,000 positions in the Navy, Army and Air Force were eliminated nationwide between April 1978 and October 1980 as the military began contracting out a variety of its blue-collar activities. DOD estimates that those personnel reductions will save the government about $130 million over the next three years.

But the unions who represent many of the government's blue-collar workers dispute this cost-savings contention, arguing that private firms will underbid in order to land a government contract, then cut corners to make a profit or raise the price of their services after the government has disbanded its in-house force.

"We've had workers laid off at bases or agencies and then rehired by the contractors to do the same work -- but at less pay, less benefits and with less protection," complained Gary DiNunno, a spokesman for the American Federation of Government Employees, the union representing the largest number of federal workers.

Federal workers who are replaced when their jobs are contracted out are entitled to severance -- one week's pay for every year of service. They can claim unemployment compensation and withdraw their retirement benefits.

This summer, following the guidelines established in an Office of Management and Budget circular, all government agencies began a detailed cost analysis of job performances.

Barring national defense or other security considerations, government officials say, many of the blue-collar jobs will be handed over to private firms who bid on them and demonstrate they can do the work for at least 10 percent less than agencies now spend to perform the work in-house.

At the Navy, operations at 370 locations are being reviewed nationwide. The Navy lab here, for example, will look at more than 100 custodial, refuse collection, audiovisual services and motor vehicle maintenance and operation jobs to see if it would be cheaper to contract them out. The Veterans Administration and the General Services Administration, two of the largest non-military agencies to employ blue-collar workers, will be surveying the work of 35,000 and 13,000 employes, respectively. At GSA alone, more than 2,200 custodians, security guards and auto mechanics in the Washington area will have their jobs reviewed.

"If you're in the private sector, you sure want these contracts, and this government is responsive to the private sector, that's no secret," said Betty Miller, a labor relations specialist with the Labor Department.

Given that climate, labor leaders such as Christopher Hill, president of the Washington Area Metal Trades Council representing 7,600 workers at nine federal agencies, are turning to Congress to argue their case that contracting out provides false savings and leads to inferior work.

But unless and until Congress takes a closer look at the government's contracting-out practices, workers whose jobs are under scrutiny have little recourse but to wait and see what happens.

"My parents always said that a government worker is secure," said Ron Kessler, 36, a heavy mobile equipment mechanic who has worked at the Navy Yard for 12 years and earns $10.81 an hour. "We break our backs trying to do a good job, and then this happens. Let me tell you, we don't tell our kids to work for the government."