The Georgia Chamber of Commerce recently mailed letters inviting its 3,000 members to a "strategy seminar" Sept. 21 on how to handle women clerical employes who "barge in noisily demanding" changes at the office.

But some letters never reached the bosses. Many were intercepted by secretaries such as Brenda Slater who opened the one dispatched to her boss at Ford Motor Co. here.

Slater did not like what she read about the "Strategy Seminar for Managing White Collar Women" and helped sound the alarm.

"Suppose you are sitting in your office one day when a group of female clerical employes barges in noisily demanding a published salary grading system, a grievance procedure and a published plan for career advancement," wrote Ernest B. Davis, the chamber's executive vice president.

"What do you do? What have or have you not been doing that set off this confrontation? How could you have prevented it?" he went on.

"I didn't really read it until a secretary across the hall came running over with the boss's invitation," recalled Slater, who said she does not consider herself a feminist. "She was yelling, 'Look at this! Look at this! We've got to do something about this.' "

The women, most of whom are not part of the struggling women's movement in the South, have launched a media protest that has won converts for an organization called Atlanta 9 to 5. That is the group targeted by the Chamber of Commerce in the letter as "militant feminists" whose "targets include any employer of female white-collar workers, the more the merrier."

"9 to 5" is a national office workers' advocacy group with 12,000 dues-paying members who provided Hollywood screenwriters with the inspiration for the script and title for the Jane Fonda-Dolly Parton-Lily Tomlin movie about outraged secretaries who tie up their boss and poison the office coffee. The movie's benefit premiere raised about $30,000 for 9 to 5, and Fonda has spoken on their behalf.

In 1973, a Harvard University secretary, Karen Nussbaum, organized the first chapter in Boston, which joined other office worker groups around the country as Working Women, opened chapters in 13 cities and now lobbies state legislatures and Washington for better working conditions.

The dilemma of low-paid clerks and tellers at Georgia Federal Savings & Loan Association, hardly radical feminists, is the kind of situation 9 to 5 has tackled nationwide. The media fallout over the chamber letter has provided an unexpected assist. It has helped galvanize women who otherwise might take little interest in such women's issues as the Equal Rights Amendment.

"The Atlanta situation is just a microcosm of what 15 million working women go through every day," said Vicki Hyde, 31, president of Atlanta 9 to 5 and a single mother who supports three daughters on an $11,000-a-year salary as a department store clerk.

"The tone of the letter struck me as so condescending to women," Slater said angrily. She contacted 9 to 5 and joined a coalition that has formed between that group and irate women members of the chamber.

At least one chamber member, Patty Herbert, owner of a photographic studio, said she plans to cancel her membership because she was so offended. "It was just disgusting," she said. "Even my husband couldn't believe it."

Tracy Turner, a public relations writer and chamber member, termed the seminar "blasphemous" and plans to turn her pen against the seminar organizers.

Protesters are trying to gain representation at the seminar, billed as an "excellent opportunity for management to prepare for, or avoid altogether, confrontations with militant feminists groups" such as 9 to 5, which is affiliated with the Service Employes International Union but is not a union.

Diane Teichert, staff coordinator of Atlanta 9 to 5, said the phone has been ringing steadily with inquiries from office workers and secretaries who had never heard of the group and wanted information on how to sign up.

Until last week, 9 to 5 had 150 dues-paying members and a mailing list of 1,500. On Wednesday night, Teichert enrolled five new members at a meeting as television cameras rolled and secretaries recounted office horror stories, swapping sweatshop tales of working for low pay with no bathroom breaks or phone privileges and a lack of respect from male colleagues.

The chamber letter advertises James Wimberley Jr. as the labor lawyer who will hold forth at the seminar. He represents beleaguered Georgia Federal, target of a 9 to 5 effort to push for higher pay and better working conditions for the bank's clerical help.

Davis took responsibility for the letter and, although he said later that he was sorry about language used in it, the seminar will go on.

He said the seminar is one of many strategy sessions designed to help companies keep unions out by tuning up management techniques, making workers happy and improving communications with employes.

But restaurateur Margaret Lupo, president of the women's Chamber of Commerce, saw it differently. "It sounds like they want to keep their feet on our necks," she said.