By now, just about everybody must have heard that banks and the government - meaning the taxpayers - will have to come up with more than $50 billion to rescue or close hundreds of insolvent savings and loan institutions.

But that loss is just the tip of the iceberg. There's also government's own vast portfolio of subsidized loans and loan guarantees that has soared above $745 billion. A substantial part is bad debt that will never be repaid.So badly are the loan programs managed that no one can put a figure on the impending losses, even though they will swell the budget deficit.

Recently, the General Accounting Office, Congress' watchdog, completed an audit of the Farmers Home Administration, which lends to farmers and rural dwellers who can't get credit at commercial banks. It found cumulative losses of $36 billion on the agency's $90 billion of loans and obligations.

Large losses also are reportred in the Federal Housing Administration's $283 billion loan guarantee program and the Veterans Administration's similar program. Both show higher default rates than normal.

The Rural Electrification Administration, whose time has passed and now is an unneeded subsidy to rural America, may lose $8 million on loans made for nuclear power plants.

Among other loans and guarantees that cause concern are those for foreign military sales, the Export-Import Bank, small business, education and student loans.

In recent years, loan guarantees have mushroomed to $528 billion, largely because of their appeal to Congress: When they are made, they have no effect on the budget; it's only when they go sour that they enlarge the deficit.

A telling point is made by Rudolph Penner, former head of the Congressional Budget Office. As he recently noted, "Many of these programs are terribly managed. There was a proposal several years ago to sell some of these assets in the private market, but no one could estimate their true worth. Records were in terrible shape. There was no way to sell these to private investors."

The main problem with government loans is that many people think they don't have to pay them back. In a way, they're right. A commercial bank can repossess a car or foreclose on a house. But when tens of thousands of borrowers fall behind on, say, rural home loans, politics forestalls mass foreclosures, and taxpayers make up the losses.

Congress should stop throwing around cheap and guaranteed loans for every perceived good purpose and start phasing out such handouts. Otherwise, the $150 billion budget deficit may reach $250 billion.