Two conservative groups which support gay marriage have criticized the GOP's stance on marriage in a full-page ad.

The ad, set to appear in Wednesday's Tampa Tribune, is sponsored by Young Conservatives for the Freedom to Marry and gay GOP group Log Cabin Republicans.

Last week, Republicans approved language in the 2012 Republican Platform which supports a federal constitutional amendment defining marriage as a heterosexual union. Republicans meeting in Tampa this week are expected to ratify the platform.

Tony Perkins, president of the Family Research Council (FRC) and the architect of the GOP platform's marriage plank, is quoted in the ad: “The institution of marriage is the foundation of civil society. Its success as an institution will determine our success as a nation.”

“We agree,” the ad continues. “That's why Log Cabin Republicans and Young Conservatives for the Freedom to Marry believe that government should stop denying marriage licenses to committed gay and lesbian families. As conservatives, we believe that the freedom to marry is directly in line with the core ideals and principles of the Republican Party. Family values means valuing ALL families.”