The senior Alexandria delegate to the Virginia General Assembly said yesterday that if former House majority leader James M. Thomson should still seek an Alexandria judgeship he will be going against the wishes of the people of Alexndria.

Democratic Del. Richard R. G. Hobson made that statement yesterday after receiving the report of a 12-member citizens committee that refused to endorse Thomson's candidacy. Thomson, leader of Northern Virginia's assembly delegation until his defeat in 1977, has been criticized by civil righs and women's organizations as a racist and a sexit.

The citizens committee, apointd by Hobson and including four blacks and five women, endorsed the candidacies of Alexandria lawyers Albert H. Grenadier and Terrence A. Sidley.

On Thursday, night, the Alexandria Bar Association also refused to endorse Thomson, picking instead Grenadier, a 52-year-old lawyer who has practiced in Alexandria since 1951.

The bar association's endorsement traditionally has been crucial to judgeship selections by the General Assembly, where Thomson served 22 years and has maintained close politicial ties with the Democratic majority.

Judges in Virginia are norinated in a caucus of the Democratic legislators and then elected by the overwhelmingly Democratic legislature. The Alexandria judgeship vacancy was created when Chief Circuit Court Judge Franklin P. Backus announced he would retire Feb. 1 from the $42,500--year position.

Thomson, who had earlier vowed to abide by the decision of the Alexandria Bar Association, left open the possibility on Thursday that he may seek the judgeship on his own. The former legislator had not decided what to do as of yesterday, according to a legal associate.

Hobson, who said he will make his decision Monday on which candiate he'll endorse, said Thomson's influence with legislators in spite of his failure to get support from the Alexandria community.

"Jim Thomson has been the Majority leader of the House for a long time. He has friends who've known him well for years. All of that is a factor. I wouldn't want to make a prediction about what is likely to happen," Hobson said.

Any member of the caucus is free to make a nomination, but traditionally the legislators have bowed to the wishes of area legislators in naming local judges.

Along with the bar endorsement, the support of the local Democratic House delegation, which includes Hobson and Del. Elise B. Heinz, is also important in the General Asembly's judgeship appointment. Heinz said yesterday she has pledged to support the candidate endorsed by the bar association.