At a meeting marked by bitter recreminations, the Alexandria City Democratic Committee Monday night expelled its treasurer, who was accused of helping groups advocating the Equal Rights Amendment to the U.S. Contitution in defeating long-time state Del. James M. Thomson of Alexandria in last month's election.

The expulsion of Marianne W. Fowler came on a 42-to-4 vote. She had been accused of violating party bylaws that forbid any committee member from supporting political candidates who are not Democrats. Fowler denied the charges.

Thomson, majority leader of the House of Delegates, was defeated Nov. 8 in his bid for a 12th two-year term following a campaign led by advocates of the ERA. Thomson has been a staunch opponent of ERA, which has never been approved by the Virginia General Assembly.

Thomson was defeated by Gary Myers a Republican lawyer who was urged by pro-ERA forces to enter the race, and by Richard R. G. Hobson, a Democrat incumbent who supports ERA.

One group active insupporting pro-ERA candidates and inseeking Thomson's defeat was Virginians for the Equal Rights Amendment (VERA). It was Fowler's role as state coordinator for VERA that upset many members af Alexandria's Democratic organization and led to last night's action.

Fowler told the committee Monday night that her support of ERA was consistent with the stated policy of both the national and local Democratic parties and that she had tried to work within the party by urging Thomson to change his mind on the ERA issue, and, when that failed, by urging other Democrats to run in the primary.

"I did not support Jim Thomson and I did this with a perfectly clear conscience based on my principles and the principles of the (Alexandria) Democratic Committee."

Fowler said it was the committee that was on trial, and added: "Does or does not the Democratic Party support the principles it so glibly tosses forth every four years in the national pary platform?"

Patrick J. holland, the unsuccessful Democratic candidate for Alexandria sheriff and a member of the party committee, said the committee had no right to judge the quality of Democratic candidates nominated by the voters in the primaries.

"The issue at hand in this committee is to elect (Democratic) candidates in the general elections. If you can't do that, if you can't support Democratic candidates, then resign from this committee," Holland said to applause.

Fowler asserted that several committee members had actively worked with the VERA group to insure victories by Hobson and Myers and the defeat of Thomson. At one point this brought a demand from the audience that Fowler name the committee members who worked against Thomson.

"How much of witch hunt do you wish to have?" was Fowler's reply.

Susan Blair, coordinator for the Alexandria VERA project, said at the meeting that Fowler had not prticipated in the campaing to defeat Thomson, precisely because of her position as a member of the Democratic committee.

"She never went door to door, she never made a telephone call, she never licked an envelope," said Blair.

Two committee members said they would resign in protest if Fowler were expelled. They are Marilyn Suskind and Thomasina Jordan.