The watchdog group Citizens for Responsibility and Ethics in Washington (CREW) filed a complaint Tuesday against House Speaker John Boehner (R-OH), alleging that he violated the law and House rules by agreeing to pay an outside law firm $500,000 to defend the Defense of Marriage Act (DOMA).

In the complaint filed with the Office of Congressional Ethics (OCE), CREW charged that Boehner had violated the Antideficiency Act, which prohibits "making or authorizing an expenditure from, or creating or authorizing an obligation under, any appropriation or fund in excess of the amount available in the appropriation or fund unless authorized by law," according to the Government Accountability Office (GAO).

"It is ironic that Speaker Boehner -- a fierce critic of government overspending -- did not hesitate to pledge half a million dollars he does not have to defend a law of dubious constitutionality," CREW Executive Director Melanie Sloan said in a statement. "It seems the speaker believes fiscal responsibility starts at home, but not in the House."

"Speaker Boehner has vowed to end deficit spending and usher in a new era of government fiscal austerity, warning Americans we need to make do with less. But apparently, the House leadership can continue freely spending money it doesn’t have," she added. "This is yet another case of do as I say, not as I do. No wonder the public is so cynical about politics."

The Speaker's office responded by accusing CREW of targeting Republicans.

"This 'complaint' is off-base and stupid to the point that it creates the appearance of partisanship by CREW," Boehner spokesman Michael Steel said in a statement. "The Speaker expects any cost to be recouped from the Obama Administration Justice Department, which should be defending the law in court. The 'anti-deficiency act' has nothing to do with this situation, as anyone with a basic grasp of the law knows."

In February, President Barack Obama decided that a key section of the DOMA, legislation passed by Congress in 1996 that defines marriage as a legal union between one man and one woman, was unconstitutional. The law prohibits legally married same sex couples from receiving federal benefits.

After declaring it unconstitutional, Obama ordered the Department of Justice to stop defending the law in court.

Boehner first contracted with the law firm King & Spalding to continue defending at least 10 DOMA cases, but they backed out under pressure from the public. Bancroft, PLLC was later retained to defend the law.

The $500,000 contract represents more than 35 percent of the Office of General Counsel's budget. "With more than two-thirds of the fiscal year having passed, the office will not have sufficient funds to pay for both its remaining salaries and expenses and the DOMA defense," according to the complaint (PDF).

Boehner could face a fine of $5,000 and two years in prison if found guilty of violating the Antideficiency Act.

With earlier reporting by Eric W. Dolan