The beleaguered savings and loan industry yesterday formally asked the government to grant emergency aid to inflation-squeezed thrift institutions by providing them with an infusion of fresh capital through low-interest loans.

The plan, adopted by the United States League of Savings Associations, calls on the Federal Savings and Loan Insurance Corp. to use its $7 billion safety fund to lend hard-hit institutions enough to bolster their net worth.

At the same time, the trade organization called for a series of new proposals to encourage saving and reduce interest rates -- including restrictions on money market mutual funds, which have sapped billions from S&Ls.

The new package, approved overwhelmingly by the trade group's executive boards late yesterday, is scheduled to be presented to the entire association membership this morning and pushed vigorously by the organization's lobbyists.

However, unlike a previous version of the plan, the subsidized loans to the institutions would not involve purchase by the government of their older, lower-yield mortgage portfolios. Instead, the aid would be in the form of a straight loan.

Rollin D. Barnard, the Denver savings and loan president who is chairman of the league, said the plan had been shown informally to Reagan administration officials, but it was "too early" to say how they feel.

Treasury Secretary Donald T. Regan told reporters last week that the administration was considering standby measures to help the industry in case of a financial crisis, but he declined to predict what measures it might propose.

Association officials said they believe the loan plan could be put into effect by federal regulatory agencies without new legislation. However, other portions of the organization's program would require approval by Congress.

The industry is in serious trouble, principally because it is being squeezed by interest rates. Institutions must pay high rates to attract cash. sYet, much of their income comes from decade-old low-interest mortgages.

At the same time, many would-be savers have taken their money out of savings and loans and put it into more lucrative investments, particularly money market mutual funds, which pay yields of 16 percent -- compared to 5 1/2 percent for S&Ls.

Wall Street analyst say investors have poured almost $20 billion into money market mutual funds since the beginning of this year. Many of these funds also offer investors check-writing privileges similar to the S&Ls'.

The plan for the emergency aid by the government calls on the Federal Home Loan Bank Board, which oversees the industry, to authorize the FSLIC to use its insurance fund for what amounts to subsidized loans to hard-hit institutions.

The loans would be made by government "purchase" of 10-year "capital certificates" issued by the troubled S&Ls -- enough for each institution to cover its operating losses and bring its net worth up to 2 percent of savings -- at a relatively low interest rate of 8 1/2 percent.

Once the institution became profitable again, it would be required to channel half its reported earnings to repayment of the certificates' principal. The transaction would not involve any exchange of mortgage portfolios, as previously understood.

Barnard said the plan would cost the government only the difference between the 8 1/2 percent the FSLIC would get from the S&L and the higher rate it could have obtained by investing in traditional markets. He estimated that would amount to $25 million a year.

The restrictions the league is seeking on money market mutual funds would effectively subject them to the same limitations that supply to the money market certificates that savings and loan institutions now may issue.

These include requiring the funds to maintain reserves equal to 12 percent of their holdings, limiting their yields to those of money market certificates and requiring them to invest a portion of their money in treasury securities.

Besides the emergency aid and curbs on money market mutual funds, the league also is calling for deep budget cuts to help lower interest rates and a series of new tax incentives designed to encourage more savings.

It also wants the governments to backtrack somewhat on last year's quick elimination of the traditional quarter-percentage-point differential that thrift institutions enjoyed over banks on interest for savings accounts.

Congress originally called for a phasing out of the two-tier interest differential over six years, but regulators speeded up that process to six weeks. The S&Ls contend they need a longer adjustment period.

Barnard described the subsidized loan proposal as an emergency measure designed only to tide beleaguered S&Ls over the current high-interest period. dHe said the other steps were necessary for the industry's longer-term health.