Unnecessarily expensive travel by government officials may cost taxpayers $50 million annually. Rep. Marty Russo (D.-ILL.) declared yesterday. The waste is caused primarily by the failure of employes to take advantage of discount air fares and to take the train for short distance trips, according to a report he cited at a hearing.

Among the examples in the report by the House subcommittee on special small business problems:

Department of Energy officials fly 90 percent of the time between Washington and Philadelphia, and between Washington and New York. The DOE office is one and a half blocks from Union Station.

In one year, Housing and Urban Development employes booked 117 flights to Philadelphia while the Internal Revenue Service had 30 flights. In June 1978 alone, 17 DOE employes flew to Philadelphia. There are even cases of employes taking taxis to Baltimore Washington International Airport to fly there.

Fewer than 10 percent of Defense Department personnel utilize discount fares, even when traveling in groups. (About 40 percent of the flying public now pays less than full fare.) Official and personal military travel costs about $500 million annually.

Almost 500 government employes do travel agent work as civilian agencies at an annual cost $3 million. Only 40 percent of their working time is spent on these functions. Total travel employes for military and civilian comes to l,526, at a cost of $8.8 million in salaries.

The purpose of the hearing was to discuss whether the prohibition on using commercial travel agents for government travel should be lifted. A General Accounting Office study ordered by the subcommittee proved in-conclusive, it found that the administrative burden and cost of doing business with thosands of outside travel agents might offset any savings in personnel costs. Yet the GAO indicated it would be willing to try outsiders on an individual agency basis provided the service could be shown to be more efficient and less costly.

Most of the session was devoted to examples of waste. The country's official travel bill in fiscal 1976 amounted to about $450 million. Rep. Russo said he thought it could be shown that taxpayers are spending between $50 million and $100 million a year more than is necessary for these trips.

Rep. Albert Gore, Jr. (D.-Tenn.) pointed out that the average travel time between Washington and Philadelphia, including taxis to the terminals, is two hours and 12 minutes by train and two hours and 15 minutes by plane.But the air fare is more than double. By adding the loss of revenueto Amtrak, the government revenue to Amtrak, the government receives an annual federal subsidy of $700 million, the total cost to the taxpayer of a plane ride to Philadelphia is $62.34, compared with $20.10 for rail. Each trip creates an unnecessary expense of $42.24, Gore said.

Even deducting the work time lost by taking the train to New York, he calculated the real cost of a plane trip is $80.14, or $37.25 unnecessary cost per trip. The three agencies mentioned above spent $48.000 in excess travel costs to these cities in one year.

Gore suggested that if federal employes were adamant about using planes when trains were cheaper, the employes should reimburse the government for the excess cost.

Airlines now receive 96.8 of the outlays for federal travel. Kathy Hartz, district sales manager for Amtrak, said that Amtrak recently was asked to remove its stock of tickets from the Energy Department. Amtrak tickets are now sold in only 29 out of 200 government agencies.

The argument for using outside travel agents is based on the perception that government employes handling travel are not familiar with discount fares. In fact, there is even a documented case of employes telling a travel clerk that federal travelers could not use discount fares.

The GAO gave the following examples: The Federal Aviation Administration spent $312,000 unnecessarily on air travel in 1976 for trainees flown to Oklahoma on individual fares. Defense trainees spent an excess of $230,000 because they didn't use excursion fares. The General Services Administration could save $306,000 a year on routine flights to Denver.

The GAO has calculated that federal agencies could have $145,000 annually if they purchased rather than leased the 172 electronic ticket writting machines they now use. Air Force officers told a trade publication they would soon begin testing a computerized system that would save the government as much as $14.6 million annually in handling travel arranements.

There is also was testimony be Amtrak supporter Gore that airlines are actually receiving federal subsidies in addition to the lion's share of travel expenses.The airlines receive free office space in government agencies . Moreover, they offer federal employes no discounts, as do hotels and rental car companies.

Current federal law prohibits paying commissions for official travel. The airlines contend that if they were obliged to pay travel agents 7 percent commission on flights they book for government officials, fares would go up. Travel agents maintain they have a right to do business with the government. They also say there would be no additional cost to the taxpayer.he taxpayer.