Descendants of the late Leonard P. Steuart, co-founder of one of the largest family financial and business empires in Washington history, have become embroiled in a bitter feud over the fate of the corporate fortune.

Elizabeth Steuart Moore, one Steuart daughter, calls the fight a "family vendetta."

Moore has filed a suit in D.C. Superior Court charging mismanagement of the Steuart business by sister Virginia Steuart Martens and her husband - legal action that is most unusual for a family that historically has preferred no publicity about its private life, extensive philanthropy or multimillion-dollar ventures.

And then the family feuding surfaced again this week in another forum, the annual stockholders' meeting of American Homeowners Insurance Co., a small Steuart firm doing business in the District.

It was at that meeting that Harry Martens Jr., husband of Virginia and chairman of the Steuarts' Imperial Investment Co. Inc., voted to oust Elizabeth's husband as a director and president of the insurance firm.

Elizabeth's husband, A. Wallace Moore Jr., had been with the company for 20 years. Another director for 17 years, Bayne Marbury, also was replaced. Elected in their place were Virginia Steuart Martens and her son, Harry Martens III.

At issue in the Steuart squabble are family holdings valued at more than $13 million at the end of 1977. Depositions in the court case have begun and a trial on Elizabeth Steuart Moore's charges against her sister is expected to start in the fall, a spokesman for Moore said.

Only one wing of the Steuart family is involved in the current fight - the daughters of Leonard P. Steuart and their husbands.

Brothers Leonard and Guy T. Steuart, who began business here with a mule-and-cart ice and coal venture in 1904, branched over the years into automobile dealerships, insurance, investment companies and petroleum. They were born in Branchville, in Prince George's County, of Irish and French descent. Their father, a farmer, died when they were young and their mother moved to the city.

Eventually, the Steuart brothers had 20 separate companies and overall businesss volume from the ventures they started reportedly surpassed $100 million by the early 1970s.

Guy Steuart died in 1958, and his heirs assumed ownership of the Steuart Investment Co., a holding company for Steuart Petroleum Co. as well as trucking, insurance, real estate, auto dealership and other ventures. This family and their businesses are not involved in the current fight.

Leonard P. Steuart died in 1966 at a time when his Chrysler-Plymouth dealership here had become the largest in the country. He left his estate - half a dozen auto dealerships, a distributing firm, taxicab companies - to his wife and two daughters.

The remaining L. P. Steuart firms, now operated by Imperial Investment Co., are at the heart of the family fight. But one of the allegations by Elizabeth Steuart Moore is that she has been shut out of family business decisions and that several Steuart companies have been sold and closed without providing her any economic return.

According to the suit in Superior Court, each Steuart daughter owns approximately the same number of shares in the faimily's Imperial Investment Co.

Virginia Steuart Martens owns close to 13,000 shares and Elizabeth Steuart Moore owns about 12,100 share out of less than 43,000 shares outstanding.

The next largest block - 10,412 shares - is in trust for the benefit of Bessie Steuart, the wife of L. P. Steuart. But these trust shares are voted by Virginia Steuart and Harry Martens as trustees - giving them effective voting control.

Lawyers for Harry Martens Jr. and Virginia Steuart Martens have told the court, that their side of the family has controlled two-thirds of Imperial's shares since 1973. Further there is agreement that Harry Martens Jr. and his wife "have controlled Imperial's board of directors."

However, there is sharp disagreement on most of the other allegations by Elizabeth Steuart Moore and her husband. Martens was not available for comment yesterday on this week's insurance company meeting or the lawsuit. A lawyer for Martens, Robert V. Smith, also not available yesterday.

But in court papers filed as a response to the suit, Smith denied the charges of mismanagement against Virginia Steuart Martens, Harry Martens Jr. and Imperial Investment Co. as well as the allegation that Virginia Martens and her husband have used Steuart business assets "for their own private gain and advantage."

Specifically, the Moores alleged in their suit, that:

Virginia and Harry Martens Jr. and Imperial Investment Co, have been engaged in "unlawful manipulation" of the family business.

They have dominated the board "wrongfully, oppressively" and have excluded the Moores "from any corporate benefits, or any voice in the management of the company."

"Unlawful actions, bad faith and breach of fiduciary duties in grossly mismanaging Imperial for their own personal gain have resulted in extreme tension, hostility and dissension in the corporate affairs of Imperial which are not likely to abate."

Imperial has paid no dividends to stockholders since 1973 whilce Martens received "excessive" annual salaries of $127,000 in 1976 and $80,700 in 1977, and also "excessive perquisities" such as club memberships and travel aboard. Meanwhile, Imperial had losses of more than $1.3 million in the two latest years and closed most auto dealerships, reducing Steuart assets.

Imperial funds were used to finance the business of a son, Harry Martens III, called Martens Chevrolet, as well as another unrelated company, Marlow Datsun.

The Moores asked the court to appoint a receiver who would liquidate and distribute remaining assests of Imperial, "to protect the interests" of the minority owners.

In response to this list of allegations, lawyers for Martens and his wife contend there is no basis for appointing a receiver at Imperial because the charges are "erroneous" and because the Moores had given their "repeated approval and ratification of all acts" alleged by the Martens to have been unlawful in previous years.

Moreover, the Martens' lawyers denied all charges of wrongdoing, and said the procedure used to establish Martens Chevrolet "was the only method available under policies . . . dictated by the Chevrolet division of the General Motors Corp." A $300,000 loan by Imperial to Martens Chevrolet "represents a profitable investment," they stated.

For these reasons, the lawyers for the Martens asked the suit be dismissed.