A top official of the Federal Home Loan Bank Board, the watchdog of savings and loans, sought bids on a half-million-dollar home loan from two dozen Washington-area mortgage bankers by sending them mailgrams signed with her name and title.

The incident began three weeks ago when Shannon Ann Fairbanks, the bank board's chief of staff, sent the mailgrams asking about the possibility of borrowing "over $500,000 . . . for a home I recently purchased in the embassy area of the District."

Mortgage lenders who received the inquiry say that, except for the size of the mortgage sought, the request at first glance seemed to contain nothing unusual. They say they sat up and took notice, however, when they got to the end of the mailgram and saw it was signed, "Warmest personal regards, Shannon Fairbanks, chief of staff, Federal Home Loan Bank Board."

"That caught our attention real quick," said Dan Coffey, branch manager and assistant vice president at Goldome Realty Credit Corp. "We are so incredibly regulated by the bank board -- it would be like doing a loan for a watchdog . . . for someone who knows how every 't' should be crossed. It makes you tense up."

Fairbanks said last week when asked about the mailgrams that use of her official title on a personal correspondence was "inadvertent and inappropriate." She said that her title accidently was added by her government secretary, Patti Gattuso.

"I told my secretary exactly what I wanted it to say. I dictated to her," Fairbanks said. "It just never occurred to me to tell her not to use my title. She's used to signing my things with my title."

Gattuso agreed that Fairbanks did not ask her to include an official title on the mailgram. "But it's normal for me to sign her title," she said. "That's why I did it."

Fairbanks said, "I was not trying to flaunt my title and get special favors. The irony of this whole thing is that I was trying to avoid any special treatment. And even if anyone tried to give me a special rate, I couldn't accept it. I'm not allowed to."

Fairbanks said she "occasionally but not often" asks her secretary to do personal favors, the sending of the mailgrams being a recent example. "If I had been conscientious, I would have made sure she did it on her own time, but I didn't. I forgot. I know people paid by the government should not do personal duties for bosses on government time. It's an important principle. It's very clear to me. Very clear."

Last week, Gattuso said that "throughout the day," on government time, she phoned in the Western Union mailgrams at Fairbanks' request. Yesterday, however, after speaking to Fairbanks and examining the time the mailgrams were sent -- between 1:20 p.m. and 1:40 p.m. -- Gattuso said that she sent the mailgrams during her lunch hour.

Fairbanks said that the cost of the mailgrams was billed directly to her own credit card and not to the government. She said that she sent written inquiries because a bank board lawyer said to leave what he called "a paper trail" indicating she had sought competitive loan bids at market rates.

The purpose, she said, was to ensure that no one could think she had misused her job in a financial regulatory office to obtain a mortgage "other than what is available to others." This week she sent handwritten letters to all who received the mailgram, saying, "The mailgram . . . was personal . . . . Inadvertently, my title and place of work were added at the end."

Although a loan officer eventually would learn of Fairbanks' position, the direct reference to her job in the preliminary stage of the mortgage process left room for wide interpretation and caused even seasoned mortgage lenders to think twice.

Said one Equitable Bank executive, who did not want his name used, "In this day and age nothing is really surprising when it comes to a credit application . . . but she has power and we would want to make sure we handled it very carefully. She probably could cause trouble."

Publicly, most of the banking officials who received the letters from Fairbanks declined to comment. But privately, several officials said they thought the letter was surprising or inappropriate.

Fairbanks has close ties to the Reagan administration. Before joining the bank board, she was a senior policy adviser in the White House office of policy development from January 1981 to May 1983.

Fairbanks, who has a masters degree in housing and public finance from Columbia University, was liaison between the White House and Reagan's committee on housing in 1981 and 1982, and she was a senior policy analyst in the 1980 Reagan-Bush campaign.

Fairbanks said that sickness and a busy schedule have prevented her from investigating terms offered by the handful of lenders who responded to the mailgram.

She said that because the sale on the house will close this month, interim financing has been obtained by a lawyer who handles financial affairs for Fairbanks and her husband, Richard Fairbanks, a former U.S. ambassador-at-large who was involved in Mideast peace talks and now is in private practice. She would not disclose the exact location or price of the house.

Fairbanks said she does not know the name of the lender providing the interim loan, which will have to be refinanced within a year.