Mitt Romney's stand on gay marriage will become an issue as the GOP race heads to New Hampshire.

Lawmakers in the state will begin debate on a measure to repeal the state's gay marriage law in January – the same month New Hampshire will hold its Republican presidential primary contest.

Critics charge that Romney, 64, has flip-flopped on the issue.

During an appearance last month on NBC's Meet the Press, Obama adviser David Plouffe said Romney has “moved all over the place” on issues, including gay marriage.

In an interview on Monday with the Nashua Telegraph, Romney said that he remains opposed to gay marriage, but favors gay rights. (Watch the video.)

“The story on same-sex marriage is that I have the same position on that I had when I ran from the very beginning,” Romney said. “I'm in favor of traditional marriage. I oppose same-sex marriage. At the same time, I don't believe in discriminating in employment or opportunity for gay individuals. So I favor gay rights, I do not favor same-sex marriage. That has been my position all along.”

GOP rivals Rick Perry, Michele Bachmann and Rick Santorum have also taken swipes at Romney.

“I would argue that Mitt Romney, as governor of Massachusetts, was to the left of Barack Obama on the issue of gay marriage,” Santorum said during an interview on Laura Ingraham's radio show.

And during an interview on the Steve Deace radio show, Bachmann accused Romney of signing “189 same-sex marriage licenses.”

The issue could also ensnare Herman Cain and Rick Perry, whose comments on gay marriage have been criticized by conservatives.

Both candidates have made contradictory statements on whether the issue should be addressed at the state or federal level.