The Alexandria City Republican Committee censured one of is members last night because he supported an independent candidate -- rather than a Republican -- for city prosecutor in last November's elections.

The censure of committee member Martin P. Claussen was the first ever issued by the city GOP organization, which has been increasingly successful in recent elections. The 49-to-12 censure vote came after a bitter debate on political loyalty.

The censure carries no penalty, and the 65-year-old Claussen, a political conservative who is on an advisory committee to GOP presidential candidate Philip N. Crane, said he will continue to be an active party member.

Claussen defended himself before the vote by calling the censure motion "a public lynching" that would "titillate . . . pagan liberal Democrats . . . Here we are fiddling around while Rome burns," he said.

The motion was brought by members Joan Moreci and Nancy Wolfford who said they had seen Claussen campaigning on election day, last Nov. 6, for indenpendent John E. Kennehan, rather than Republican Barry R. Poretz. Republican rules require party officials to support only Republican candidates.

Poretz lost the closely fought race for commonwealth's attorney to incumbent Democrat John E. Kloch by a 6,436 to 5,250 margin, with Kennehan receiving 2,277 votes.

Moreci told the group last night that Poretz "could have won" if Kennehan had not taken votes away from him. Morcei was Poretz' campaign manager, but denied before the meeting that revenge was involved in her censure motion.

Under questioning, Claussen initially called the question of whether he had actually supported Kennehan "a moral judgement." Later he acknowledged supporting "my old friend" Kennehan, a Republican who ran as an independent.

The vote came party member Ellen Tabb urged that reporters be thrown out of the meeting, because she did not want the party to "air its dirty linen in public." Chairman Nancy McCabe rejected the suggestion.

Republicans currently hold three of the city's seven City Council seats, one of two state delegate seats, and a sate Senate seat. City Councilman Carlyle C. Ring, Del. David G. Speck, and State Sen. Wiley F. Mitchell Jr. all voted to censure Claussen. Other elected Republicans were absent.