Expense account limits will jump by as much as $51 a day next month for federal government travelers, who are expected to spend 25 million days and $1.6 billion this year on the road for Uncle Sam.

The new regulations raise the maximum per diem for food and lodging, now $75, in most of the 400 cities ranked by the General Services Administration by their costs. New York and Atlantic City, N.J., top the list with a rate of $126.

Travelers to cities not on the list will be allowed $50 per diem, and those sent to Alaska, Hawaii, Puerto Rico and the Virgin Islands will be reimbursed under a different schedule.

Changes in the federal per diem rate have a major impact on private companies that follow the government's expense account lead, as well as hotels and motels that charge special government rates for employes and restaurants in frequently visited cities and near government installations. Many government travelers have complained that the current rates don't cover their legitimate costs.

But the new rates are accompanied by a freeze in travel dollars for most agencies. That means that although federal travelers will be reimbursed at a higher rate, fewer trips will be authorized.

Washington, formerly a $75-per-day town, goes to $112 under the new guidelines, breaking down to $79 for lodging and $33 for meals and miscellaneous expenses.

The lowest per diem rate for a state capital, Pierre, S.D., goes up from $50 to $56. Government employes traveling to Dallas-Fort Worth can spend up to $107 per day while those sent to Houston will be limited to a per diem rate of $96.

Government employes sent to Los Angeles for temporary assignments will get $110, while those toiling in Palm Springs and San Diego will be held to $100 a day, and San Francisco will become a $95-a-day town.

Federal workers sent on overnight trips to Annapolis can spend $88 a day, while those detailed to Columbia, Md., will get $106. Baltimore and Frederick, Md., will have $75 limits.

Auditors, inspectors and other federal employes sent to Ocean City, Md., can spend up to $99 per day while those staying 30 miles away in Salisbury, Md., will have a $69 limit under the newly tuned GSA regulations.

The per diem range for Virginia cities outside the Washington area goes from $58 for Lynchburg and Covington to $76 for Charlottesville and $80 for the Norfolk-Virginia Beach Tidewater area.

Civilian federal workers sent to Philadelphia will have up to $105 per day to spend, while those to Harrisburg, Pa., $83, and those to Pittsburgh, $84.

Cleveland will have the highest rate in Ohio, at $84 per diem; travelers to Dayton will be allowed $78 and those to Cincinnati, $75.

Outside of New York City, per diem in the Empire State will range from $57 in Catskill to $82 in Syracuse.

Minneapolis/St. Paul will have a $75 per diem limit, while Boston will have a $108 limit, less than the $118 rate established for Martha's Vineyard and Nantucket.

The rates do not cover the Postal Service, the government's largest agency, nor military personnel. Rates for those employes are generally much lower than the GSA levels.

GSA officials said that if the Office of Management and Budget had not ordered a freeze on travel funds, the government's per diem expenditures would have jumped by $222 million over the next year.

Federal officials say they have no idea how many employes actually travel for the government on business, but they say the largest number of travelers are Defense Department civilian workers.