A group of conservatives who support gay marriage have said they are disappointed with the Republican Platform's stance on marriage.

On Tuesday, the Republican National Committee's (RNC) platform drafting committee approved a marriage plank in the 2012 Republican Platform which supports a federal “constitutional amendment defining marriage as the union of one man and one woman” and “campaigns underway in several other states to” amend their constitutions to define marriage as a heterosexual union. The platform also criticizes President Barack Obama's decision to no longer defend the Defense of Marriage Act (DOMA) – the 1996 law which bars federal agencies from recognizing the legal marriages of gay and lesbian couples – in court.

Republicans will ratify the platform at next week's convention in Tampa, Florida.

“As conservatives supporting the freedom to marry, we understand there are divergent opinions on marriage among conservatives and within the Republican Party,” the group Young Conservatives for the Freedom to Marry said in a statement. “Even so, there are a number of things we all agree on.”

“Given these shared beliefs about marriage, we are very disappointed the Republican platform includes specific language that opposes marriage for same-sex couples.”

The group said it would continue to work on building support for marriage equality from within the party.

“As conservatives, we believe that the freedom to marry is directly in line with the core ideals and principles of the Republican Party – less government, more individual freedom, personal responsibility and the importance of family.”