The real estate industry took its campaign against the Reagan administration's "user fee" proposals to the Senate housing subcommittee this week in an attempt to reverse the setback it suffered in the Budget Committee three weeks ago.

Industry officials are reasonably confident that they can block the proposals, which they argue would raise the cost of housing, especially for low- and moderate-income home buyers. But they are clearly alarmed by the Budget Committee's last-minute decision to include the fees in its budget resolution despite having specifically voted them down in earlier tallies.

"You have suggestions from the Senate Budget Committee. You do not have the requirement to find the funds from user charges or any other program that they suggest," Jack Carlson, chief economist of the National Association of Realtors, told the housing panel at a hearing Monday.

"Your only requirement is to come up with the dollar amount that the Budget Committee has come up with. What we're arguing here is, at least I am, that there are some other lower-priority programs to take those cuts," he said.

Carlson and other industry witnesses got a sympathetic hearing from several Democratic members of the subcommittee. Sen. Jim Sasser (D-Tenn.), who offered an amendment, accepted during markup, that would have eliminated the fees, said that "unfortunately the will of the bipartisan majority of the Senate Budget Committee was wiped out in one stroke" with the adoption of a substitute offered by Chairman Pete Domenici (R-N.M.).

But Republicans were non-committal, with subcommittee Chairman Chic Hecht (R-Nev.) saying pointedly, "We have hard choices to make and we are here to make them."

The industry's position, as presented by the heads of the Federal National Mortgage Association, the Federal Home Loan Mortgage Corp. and the Mortgage Bankers Association of America -- in addition to Carlson -- is that the fees will add significantly to the cost of mortgage money, and thus to the cost of buying a home, and that these costs will fall hardest on lower-income buyers.

The administration is proposing to raise fees for VA and FHA loans to five points -- a point being equal to 1 percent of the loan balance -- though the Budget Committee recommended only 3.8. Currently, the VA fee is 1 point and the FHA is already 3.8.

It also wants to charge a fee to Fannie Mae and Freddie Mac, among others, for use of, in effect, the federal government's name when they enter the credit markets.

Government National Mortgage Association's guaranty fee would also be increased.

For Fannie Mae, which has suffered in recent years from the burden of its large portfolio of old, low-interest mortgages, the fees on borrowing would be particularly burdensome, according to its chairman, David O. Maxwell.

"If Fannie Mae is forced to swallow" the fees, which could amount to $40 million a year, Maxwell told the panel, "we will find ourselves in grave jeopardy."

If, on the other hand, the market allows these fees to be passed on to consumers, "that means the cost of a home will rise," Maxwell said.

Robert Spiller, head of the Mortgage Bankers, told the committee that in market conditions that prevailed last week, the full five-point fee, coupled with discount points -- to bring the loan's yield to market -- and lender fees, would mean that the borrower of the average-sized VA loan of about $55,000 would have to pay more than $7,000 up front.

Or if it were added to the amount of the loan, which is usually 100 percent of the purchase price in the case of VA, "we are letting that person start out with a loan that is about . . . 12 percent greater than the value of the house," Spiller said. "This simply increases the opportunity for bankruptcy and foreclosure and everything else," he said.

Several witnesses also emphasized that the fees tend to compound because they hit the same programs but at different places, falling on the borrower directly up front and indirectly in additional costs imposed on the secondary market where most loans, particularly FHA and VA, are sold.

Maxwell noted that at 3.8 percent, the payments on a $50,000 VA loan would rise from $553 a month to $574. When fees imposed on Fannie Mae are added, the payment would climb to $584 for the same loan. Over the life of the loan, the added cost would amount to $11,160.

After the hearing, several industry sources noted that the various programs have broad constituencies on Capitol Hill, and even if the Republican-controlled Senate endorses the fees, it is unlikely the House will.

However, these sources, pointing to Carlson's offer to identify "lower priority" programs, worried that the various components of the housing industry might begin to offer each other's interests as candidates for cuts. That would make it easier for Congress to do things the industry doesn't like -- particularly when tax measures are considered.

On the other hand, hard-line defenses of all real estate's benefits will be difficult in view of the large federal deficits, and the trick will be to appear cooperative while giving up as little as possible.

"It's a delicate situation," said one.