Mitt Romney is being called on to distance himself from the National Organization for Marriage (NOM), the nation's most vociferous opponent of gay marriage.

In an op-ed published Saturday in the Guardian, GOP rival Fred Karger called on Romney to repudiate the group and its pledge he signed promising to work against marriage equality.

Karger pointed to recent revelations that the group plotted a strategy to pit minorities against gay marriage supporters in arguing that NOM is “unethical.”

“[W]e now have the proof that NOM is an unethical and deceitful operation,” Karger wrote.

“Ron Paul and I remain the only two active candidates who refused to sign NOM's marriage pledge,” he added. “In the final two and a half months of this long and hard-fought campaign for the Republican nomination for president, let's work together toward equality for all Americans.”

NOM's 5-point marriage pledge asks signers to support a federal constitutional amendment banning gay marriage, defend the Defense of Marriage of Act (DOMA) in court, appoint judges and an attorney general who will “respect the original meaning of the Constitution,” appoint a presidential commission to investigate the “harassment of traditional marriage supporters,” and back legislation that would allow a ballot question on the issue for voters of the District of Columbia.