The National Organization for Marriage (NOM), the nation's most vociferous opponent of gay marriage, ended 2012 with a $1 million deficit, tax records released this week show.

NOM publicly released its Form 990 tax returns as required by law on its website. However, NOM's website offers no navigation to its Financial Reports page.

NOM is best known for its involvement in Proposition 8, California's now-defunct constitutional amendment limiting marriage to heterosexual couples, approved by voters in 2008. Passage of Proposition 8 propelled NOM to the national spotlight and fueled the group's growth as it became involved in similar battles throughout the nation.

NOM racked up loses in 2012 as voters in four states – Maine, Maryland, Washington and Minnesota – approved ballot measures allowing gay couples in those states to marry. NOM contributed to each of the state campaigns working against marriage equality.

The group's political advocacy arm ended 2012 more than $2.7 million in the red, while its education arm was in the black with just over $1.6 million.

Unnamed donors gave NOM more than $14.5 million in 2012, $9.4 million of which went to the group's political arm.

On Monday, the Human Rights Campaign (HRC) filed a compliant after it was unable to obtain a copy of the group's Form 990.

“Federal law requires organizations to publicly release their 990s the same day an in-person request is made,” HRC wrote in a blog post. “As a result, HRC has filed a complaint with the IRS in order to compel NOM to abide by the law.”

Fred Karger of Rights Equal Rights made a similar claim, saying that a representative from his group was turned away on Friday.

NOM President Brian Brown responded in a blog post, calling HRC's complaint “frivolous.”

“NOM fully complies with federal law regarding the public availability of our Form 990 tax return,” Brown said. “Our 2012 Form 990 was mailed to the IRS on November 15th as required by law. It is available for public inspection on the NOM website.”