House speaker John Boehner is being criticized from both sides over his defense of the Defense of Marriage Act (DOMA).

On Monday, House sponsors of a bill which would repeal the 1996 law which defines marriage as a heterosexual union for federal agencies filed a third request with Boehner's office asking for members to be briefed on the status of the defense.

“[W]e have long believed that DOMA is unconstitutional,” the letter states. “There simply is no legitimate federal interest served by denying married same-sex couples the federal responsibilities and rights that other married couples receive, and the harm caused to these families is unjustifiable. Two federal courts have agreed, and it is no longer credible to claim that the law is not constitutionally suspect.”

The letter – which is signed by Representatives Jerrold Nadler of New York, Barney Frank of Massachusetts, Tammy Baldwin of Wisconsin, Jared Polis of Colorado, David Cicilline of Rhode Island and John Conyers of Michigan – also states that “the materials and arguments being made to defend the law do not withstand the test of time or scrutiny.”

The Republican-led House last year ordered the House Bipartisan Legal Advisory Group (BLAG) to defend DOMA after President Barack Obama instructed the Department of Justice (DOJ) to no longer defend the law in court. BLAG authorized up to $1.5 million and hired attorney Paul Clement to defend the law.

At the time, gay marriage foes said they were elated with the decision, claiming that the Obama administration's defense of the law was purposefully weak. Conservatives, however, now say they are becoming increasingly disappointed with the law's new stewards.

“They hired Paul Clement, and they think their job is done. While the Obama administration ignores DOMA, Speaker Boehner has forgotten that the checks and balances also include Congress,” Tom McClusky, senior vice president of the Family Research Council, told Congressional Quarterly.

The increasing pressure comes as oral arguments are set for next week before the 1st U.S. Circuit Court of Appeal to review a lower court's ruling declaring portions of the law unconstitutional.

An unnamed aide to a committee Republican explained that Republicans are becoming increasingly concerned about alienating voters.

“There is a debate in the Republican conference on whether defense of marriage is a winning issue politically,” the aide told CQ.

Brian Moulton, the legal director of the Human Rights Campaign (HRC), the nation's largest gay rights advocate, sounded a similar sentiment.

“Republicans are cognizant of where the public is moving,” he said. “The Speaker's defense of the law helps us show the harms that the law has caused. … At the end of the day, his action perpetuates the harms.”