BOSTON — The group fighting to reduce penalties for marijuana possession in Massachusetts charged yesterday that opponents are misrepresenting their ballot question as a referendum on legalizing marijuana, rather than its intent to reduce penalties for small amounts of pot.

Whitney Taylor, campaign manager of the Committee for Sensible Marijuana Policy, said a radio ad this week misrepresented the referendum question.

“This ad goes beyond misstatements, spin or opinion and blatantly lies about what Question 2 would do if passed,” Taylor said. “The opponents of Question 2 are trying to dupe the voters of Massachusetts into thinking that Question 2 is something it’s not.”

Question 2, a voter referendum on the Nov. 4 ballot, would decriminalize possession of up to an ounce of marijuana, instead imposing a fine.

Vote No on Question Two, a collection of law enforcement and civic organizations, purchased the ad that said “legalizing marijuana will have a disastrous impact on thousands of families living in Massachusetts.”

William Breault, the voice in the ad and chairman of Main South Alliance for Public Safety, a Worcester public-safety advocacy organization leading the fight against the question, said he had no qualms about the ad’s language.

“If legalize helps us to get the public’s attention, we will use it,” Breault said. “We have not told (supporters of Question 2) what to do, so they shouldn’t tell us what to do.”

Breault said he felt comfortable about the language in the ad, because he believes that the pro-marijuana committee, which received $400,000 from billionaire George Soros in 2007, ultimately wants marijuana users to face no penalties.

“Soros is the sugar daddy of the legalization movement,” Breault said. “Question 2 supporters are a carefully camouflaged, highly intelligent elitist group with the goal of legalization.”

Taylor, however, said Breault’s claims are a further distortion of facts, saying Soros has never embraced legalization.

“Soros contributed money so that this issue would be discussed and debated based on facts,” Taylor said. “Unfortunately, our opponents just want to bring up red herrings rather than debate the actual issues.”

Financial support for the ad in question came from Save Our Society From Drugs, a non-profit organization against lenient drug policies based in St. Petersburg, Fla. Calvina Fay, the group’s executive director, said that Massachusetts citizens have asked for support in fighting Question 2 and believes the ad was accurate.

“When you decriminalize drugs you are essentially legalizing them,” Fay said.

This is not the first time the pro-marijuana committee has accused their opposition of breaking the rules.

In September, Question 2 supporters filed complaints with Attorney General Martha Coakley’s office, charging that the Massachusetts District Attorney’s Association distributed false statements about the ballot question on its Web site.

Taylor’s group also filed complaints with the Office of Campaign and Political Finance charging the Coalition for Safe Streets, another opposition group, with campaign-finance violations.

The AG’s office threw out the charges made against the district attorney’s association, but no decision has been released on the campaign-finance charges.