Ghostwriting for Uncle Sam has become a multimillion-dollar business. Nobody knows for sure its size and scope. But it is a heck of a lot bigger than a breadbox.

An estimated four of every 10 reports that the federal agencies send Congress as their own are, in fact, written by people who do not work for Uncle Sam, except as consultant ghostwriters.

Federal agencies are paying outsiders millions to write up congressionally mandated reports designed to tell the legislative branch of government what the executive branch is doing. It is not known if Congress hires its own outside experts -- ghostreaders -- to study and digest the reports. What is known is that the taxpayers foot the entire bill.

In a spot check of the report-writing habits of seven large and small federal departments, the General Accounting Office found that 40 percent of the products they send Congress under their own by-lines are written in whole or part by outsiders.

Between 1977 and 1979 the seven agencies spent $17 million for the ghostwritten products. Several explained to GAO investigators that the expenditures were necessary because nobody in government has the time or talent to do them. The U.S. government is the nation's largest single employer with 2.7 million workers, many of them presumably able to write a report on what they and their agencies do.

The outfits spot-checked by GAO are: Environmental Protection Agency; Department of Transportation; Federal Communications Commission; Federal Trade Commission; National Aeronautics and Space Administration and the Nuclear Regulatory Commission.

GAO's report was made for Sen. David Pryor (D-Ark.). Pryor, who heads the Senate Civil Service subcommittee has the feeling the Uncle Sam employs too many outside experts doing work that should be done in-house. In the case of the reports required by Congress, Pryor questions the legality and wisdom of having outsiders prepare work which agencies send on, under their own by-lines, advising Congress of their progress.

EPA, DOT and HUD, for example, told the congressional watchdog agency that in most cases they had to spend money on outside help because of "limited resources and time constraints" or because of "lack of special expertise." In other words their people didn't have the time or talent.

Although everybody needs outside help sometimes -- maybe to unstop the bathroom or move to another state -- many federal workers believe the government is suffering a runaway consultant problem.

Several interesting questions come to mind. If seven agencies spent $17 million during a two-year period, what is the ghostwriter total governmentwide? mAnd what is the government -- which last year spent 33,334,637 hours training people -- training its people to do?

The report is less an indictment of the typical career bureaucrat than it is of the top management and a system which decides it doesn't have the time or money to do a job but does have the time and money to hire outsiders to do it.