As the Reagan administration grapples with soaring deficit projections, one budget item that is rarely mentioned is the huge number of lawsuits pending against the federal government.

No one is sure exactly how much those suits could ultimately cost. But in the area of torts alone -- cases in which individuals or companies sue the government for damages -- plaintiffs currently are seeking $40 billion from the federal government.

The government would never actually lose that amount. Plaintiffs always ask for more than they expect to win, and many of the lawsuits will be unsuccessful. But whatever the final amount, it could be considerable.

Standing between the government and those expenses is the Justice Department's civil division, a group of 300 lawyers who serve as attorneys for most of the government, aided by about 600 lawyers in U.S. attorneys' offices across the country.

The cases run the gamut from multimillion-dollar claims over illnesses allegedly caused by exposure to asbestos, radiation, or the herbicide Agent Orange to suits seeking damages for alleged government negligence in air crashes or oil spills.

For example, the Air Florida crash here last January produced dozens of lawsuits involving the government. Mark A. Dombroff, who heads the civil division section that deals with those cases, said that a "worst case" scenario would involve the assessment of $50 million in damages against the government in that incident.

Dombroff said, however, that he does not expect to lose in most of those suits.

The civil division also handles all the cases in which government employes are sued as well as the tens of thousands of cases involving loopholes in the laws that govern the distribution of money under the government's many benefit programs. In these cases, the lawsuit is likely to involve a squabble over a couple of hundred dollars, but the precedent could lead to a loss of hundreds of millions of dollars for the government.

One pending lawsuit involves the regulations under which the government reimburses hospitals for certain expenses.

The plaintiffs are demanding that the government reimburse the hospitals for patients' telephone calls. The Justice Department insists that Congress never meant to include that sort of payment.

"It may not sound like much, but it can amount to $200 million a year. And why shouldn't patients pay for their own phone calls?" said J. Paul McGrath, the assistant attorney general in charge of the civil division.

McGrath said billions of dollars are involved in lawsuits in the entitlement area. Pending litigation involves such difficult issues as which government employes should get hardship or hazardous duty pay and whether the government can differentiate between male and female employes in wages and benefits.

In the health care area alone, McGrath said there are more than 20,000 cases pending on Social Security disability claims.

To deal with the situation, McGrath has started a process by which government officials get together every six months to evaluate the outstanding claims against the government and to determine what can be done.

The entitlement cases are of particular concern. McGrath wants to determine whether Congress can close loopholes that Justice officials say were never intended to be there.

McGrath is also considering seeking legislation to substitute the U.S. government as the defendant in cases where U.S. employes are sued in connection with their official duties. There are 50 to 60 of those cases being filed every month.

"So many suits are being brought against government officials that the feeling is that it interferes with effective management," McGrath said. "And if someone has a valid claim, he wouldn't be able to recover from most government officials anyway. Most of them don't have much money."

Having just completed his second six-month evaluation meeting of the division's cases, McGrath says it is too early to tell just what can be accomplished in terms of asking Congress to close some of the loopholes. But with 28,000 cases involving the government already in the courts and lawsuits being filed all the time, McGrath calls it "just a matter of good government" to make an effort, even on the smaller cases.

"It's the kind of thing people don't notice, but it adds up," he said. "A given suit may involve a few dollars or a few thousand dollars, but the overall impact can be in the tens of millions of dollars or more."