Republican candidate for Congress John F. Herrity, has charged in a campaign letter mailed this week that his incumbent Democratic oppoinent voted against penalties for child pornographers and in favor of spending tax money on homosexuals.

Herrity's foe, Rep. Herbert E. Harris II, yesterday called the accusations "lies" and said they constitute the "last-minute smear campaign" that he has feared from his Republican challenger since the campaign began.

With each candidate claiming the other is growing desperate in the remaining days before next Tuesday's election, the race in Northern Virginia's 8th District yesterday began fulfilling predictions that it would degenerate into name-calling and bitter accusations between two long-time political enemies.

"Herbert Harris voted against stiff penalties for those involved in the procurement of children for children pornography," states Herrity's campaign letter, which was mailed to 3,000 voters this week and which claims that "the burning issue of this campaign can be stated simply - Is the family to survive, is life to be sanctified?"

Herrity, said yesterday that the letter "speaks for itself."

"It is not a smear. These issues are burning issues for some people," Herrity said.

Harris yesterday accused Herrity of "taking votes that make sense and perverting them to the point of total misrepresentation. I've never in my campaigns been involved in this kind of malicious mudslinging activities."

Harris said that he voted for and is a strong supporter of strict penalties for child pornographers. He said the vote on which Herrity bases his accusation was "strictly a procedural vote that would have tied the hands" of House-Senate conferees in writing the child pornography bill.

"It had nothing to do with passage of the pornography legislation," Harris said. He said any interpretation of that vote that painted him as an opponent of the legislation was a "lie."

Herrity said yesterday that he has a right to refer to his opponents' voting record and that his opponent has the obligation to explain that record. In an interview, he did not challenge Harris' interpretation of the votes.

Herrity's campaign letter also accuses Harris of using "our tax dollars in defense of homosexual rights" and Herrity yesterday distributed a Gay Activist Alliance candidate rating sheet that showed greater gay support for Harris than for Herrity.

"These (gay) people have endorsed Mr. Harris," Herrity said "Perhaps that does have some influence on his voting record. You'll have to ask him about that."

Harris, a two-term incumbent, said that he voted in 1977 against a bill that denied legal assistance in disputes over gay rights because the same bill would have denied legal assistance to "someone victimized by homosexuals." Herrity said yesterday he did not dispute Harris' interpretation of the vote."

"It is a great disappointment to me that my opponent's campaign has degenerated to this," Harris said.

Both Herrity and Harris, who had traded more benign insults during the campaign before yesterday, served on the Fairfax County Board of Supervisors during the early 1970s. At that time, according to board members, the two often tried to embarrass and humiliate each other. Herrity is now chairman of the county Board Supervisors.

Harris claimed yesterday that Herrity brought up the child pornography and homosexual issues as a "cover-up for the "real" issues in the campaign, namely, support for the Metro system and the fight against the commuter tax.