Mayor Bloomberg’s decision to make New York the first city to provide universal access to emergency contraception is a betrayal of Republican Party principles and an affront to New York’s restive social conservatives, the mayor’s Republican opponents said yesterday.

At an afternoon fund-raising event at Rockaway Beach, one of the Republicans opposing Mr. Bloomberg, Thomas Ognibene, a former City Council minority leader from Queens, expressed a profound displeasure with Mr. Bloomberg’s decision. Mr. Ognibene said the initiative was promoting “another form of abortion” and bolstered his argument that the mayor is part of the “extreme left wing.”

Last week, at a luncheon of the National Abortion Rights Action League – at which he received the “Champion of Choice” award – Mr. Bloomberg unveiled a plan to spend $1 million in city money to extend to any woman who asks for it a prescription for the “morning-after pill.” What is known as Plan B emergency contraception is FDA-approved, and abortion-rights activists say it is a contraceptive, not to be confused with the “abortion pill” RU-486.

Yet while Plan B does work to prevent the formation of an embryo, it can also prevent implantation of an already-fertilized egg. Thus, to those who believe that life begins at conception – as many religious New Yorkers do – Plan B is an “abortifacient,” insofar as it destroys a human life they believe was created at the moment of fertilization.

As such, Mr. Ognibene said, the mayor is using taxpayer money to finance something many New Yorkers find morally reprehensible. Coupled with Mr. Bloomberg’s stance in favor of same-sex marriage, Mr. Ognibene said, religious and socially conservative voters – particularly Catholics, Orthodox Jews, and evangelical Hispanics – “are simply turned off by Mayor Bloomberg,” an aversion Mr. Ognibene said may cost the mayor the Republican primary.

It may do greatest political damage to the mayor in the Republican stronghold of Staten Island, a local anti-abortion activist, Gene Cosgriff, said.

Given the area’s large Catholic population, “Staten Island is a very pro-life place,” he said.

“Our tax dollars are no different from anyone else’s tax dollars,” Mr. Cosgriff added. “If they’re going against our moral, Catholic, Christian beliefs – such as to kill babies before they’re born – then we have a right to speak up.”

Mr. Cosgriff said he and several other Staten Island conservatives would speak up on primary day by opposing Mr. Bloomberg and his policies, which, Mr. Cosgriff said, “are promoting the culture of death” that an overwhelming number of voters rejected in the 2004 presidential election.

As he raises money and gathers signatures to get on the primary ballot, Mr. Ognibene said, he plans to take advantage of the mayor’s positions on abortion and gay marriage. “These are the core issues of my conservative candidacy,” Mr. Ognibene said yesterday. The third Republican mayoral candidate, Steven Shaw, an investment banker, also attacked the mayor’s initiative yesterday.

“It absolutely sends the wrong message,” Mr. Shaw said. “The way we prevent unwanted pregnancies is for people to take responsibility for their sexual behavior, not by just throwing another subsidy at the problem.” In addition to the $1 million for emergency contraception, Mr. Bloomberg pledged $2 million for other family-planning programs. According to his spokesman, Edward Skyler, those initiatives do not include abstinence education.

That omission did not sit well with some members of the Rockaway Republicans, a club that participated in Mr. Ognibene’s event yesterday. Its chairman, George Greco, and president, Tom Lynch, said that regardless of one’s position on abortion or emergency contraception, the mayor’s proposal was undermining the principles of personal responsibility central to the Republican Party platform. Mr. Greco suggested that the money would be better spent on abstinence education, so that New Yorkers could learn the lessons of self-discipline that would obviate the need for emergency contraception.

In response to the mayor’s critics, Mr. Skyler said in an e-mailed statement: “Mike Bloomberg is a pro-choice Republican and is hardly alone in that group.”

The statement added: “He believes women should be in control of their own bodies and if mayoral wannabes attack him over it, it doesn’t bother him in the slightest.”

The mayor’s position is, however, bothersome to the chairman of the state Conservative Party, Michael Long, who said he was “appalled” by the mayor’s emergency-contraception plan.

He said that, given the challenges Mr. Bloomberg faces in a Republican primary, the mayor’s family-planning initiative was politically unwise.

Last week, the Queens County Conservative Party endorsed Mr. Ognibene, and Mr. Long said he expected the four other county organizations to follow suit shortly.