The Equal Employment Opportunity Commission, stressing that it remains committed to eliminating discrimination despite recent policy changes, filed class action lawsuits against three large employers yesterday, charging that they discriminate against women and minorities.

The suits were filed against Citizens Bank & Trust Company of Maryland; PHH Group Inc. and Peterson, Howell and Heather Inc. of Maryland, and the Panduit Corp. of Chicago.

According to Clarence Thomas, chairman of the EEOC, the companies, if found guilty, will be required to change their hiring practices and award back pay that could amount to "several million dollars in each of the three cases."

Citizens Bank was charged with "discriminatory hiring practices that go straight to the top" since 1972. According to the EEOC, the bank put women and blacks in low-level positions and made assignments to branches on the basis of race, assigning blacks to branches in black areas.

The EEOC charged that the truck-leasing firm, PHH and Peterson, and its parent company, Howell and Heather, had sought since 1972 to foster "an image as a white, high-powered operation," by having its mostly white, male work force do the company's recruiting. The result was the hiring of more white men, EEOC officials said.

EEOC charged Panduit, a manufacturer of electrical devices, with turning down blacks and women since 1977 for jobs for which "non-minorities with fewer qualifications were hired," and recruiting from zip code areas where virtually no blacks live.

Spokesmen for the companies disagreed with the charges and pledged to contest them in court.

"These cases are examples of this commission's program to file strong court cases and to undertake a more vigorous litigation program through individual lawsuits and class action cases," said Thomas at a news conference announcing the filings.

Thomas said the cases are proof that the EEOC is "stronger than ever as an enforcement agency" because of the reorganization of its litigation and compliance offices since he took over the commission under President Reagan.

"It's almost always assumed that we inherited a well-run machinery, and that's not the case," Thomas said, explaining that since he took control in May 1982 the agency had been "preparing for the aggressive enforcement program we have begun to undertake."

In February the commission announced it was moving away from broad, class action complaints against large employers and entire industries in favor of more tightly focused cases involving specific victims of discrimination. At that time, Thomas said the purpose of the new policy was to have EEOC function as a law enforcement agency, checking verifiable complaints of discrimination by individuals instead of pressing for relief for entire classes of employes.

That pronouncement brought criticism from Congress and from EEOC's main nongovernmental monitor, Women Employed. Anne Ladky, head of that group, said:" Our view is that, by every statistical measure we use to monitor their performance, EEOC's enforcement activities have declined dramatically . . . . We just don't see any evidence of systemic or class action cases going on in this administration . . . .The Thomas EEOC is a disgrace."

Eleanor Holmes Norton, who ran the EEOC under the Carter administration, disputed Thomas' implication that she had left the agency in disrepair.

"The same congressional committees, public interest groups and business groups that praised our term at EEOC have had nothing but criticism for Mr. Thomas," Norton said. "Let him answer for the growing backlog [of cases] and the huge reduction in cases filed in court."