Federal deregulators of the savings and loan industry have botched the job so badly that a recovery in the housing sector will be delayed even if interest rates fall in 1982, a savings and loan spokesman testified yesterday.

One recent regulatory action, in fact, will wipe out between 20 and 30 percent of the benefits S&Ls hoped to get from the much-touted All Savers certificates, said James Christian, chief economist at the U.S. League of Savings Associations.

Christian told the House Banking subcommittee on housing that federal regulatory policy has increased S&Ls' cost of borrowing money by far more than it has raised the amount S&Ls can charge for loans.

"Deregulation is supposed to remove government restraints on the operation of free markets and minimize the burden of regulatory costs. For savings and loans, in particular, deregulation has been extremely unbalanced," Christian told the panel.

S&Ls were paying out high rates of interest on six-month money market certificates years before adjustable rate mortgages were allowed to increase the associations' yield on loans, he said.

In addition, a recent action allowing S&Ls to pay higher interest rates on passbook savings accounts "will affect no one's decision to hold passbook deposits but . . . will increase savings cost by roughly $500 million a year," Christian told the subcommittee. This action will offset up to 30 percent of the cost relief of the tax-exempt All Savers certificates S&Ls began to offer this month, he said.

"The damage already done to the housing-delivery system is sufficent to delay recovery of the housing sector in 1982 even if interest rates fall," Christian concluded. "Many home builders have gone out of business. They cannot immediately resume production."

Kenneth T. Rosen, a professor at the University of California at Berkeley, gave the subcommittee one of the most pessimistic views in a long line of grim predictions the panel has heard over four days of hearings on the future of the housing industries.

"There will be a complete collapse of the housing industry as a whole" at the end of this year, Rosen predicted.

Citing the record-low number of housing starts this year, he said the figure will go even lower. "The building industry is shutting all production," and there will be a large number of bankruptcies, "more than anyone expects," Rosen told the panel.

"The only surprising fact . . . is that, given the high interest rates now being experienced, there is any housing activity at all," he concluded. "It is likely that even the remaining low level of activity will collapse in response to the present record-high interest rates plunging the housing sector into an outright depression and the overall economy into a severe recession."