It’s been three years since the House committee tasked with legal oversight of the US Department of Homeland Security actually had a hearing on the agency’s actions—a lapse that Democratic members of Congress are calling “indefensible.”

The House Judiciary Committee is supposed to vet the legality of the department’s policies, including the conduct of Immigration and Customs Enforcement and the border patrol, which are carrying out Donald Trump’s immigration policies. The political party that controls the House and Senate chairs their congressional committees, and sets the committee’s agenda.

But the committee is “failing to exercise” its responsibilities, say Democratic committee members in a letter today (July 11) to chairman Bob Goodlatte, the Virginia Republican. That failure has “grown even more indefensible as the nation has watched the horrors caused” by Trump’s “zero tolerance policy” that’s separating families at the US-Mexico border, the letter continues.

The Democrats’ letter comes as the committee is involved in a bitterly partisan fight over its oversight of the Federal Bureau of Investigation, including its investigation into Russian meddling in the 2016 election. Goodlattte accused a former FBI agent who refused to testify in front of the committee this week of having “something to hide” yesterday, and other Republican members called the agent “pathetic” and part of “the swamp” today on Twitter.

While the FBI fight rages, the committee isn’t examining the Department of Homeland Security’s role in what Democrats have labeled “government sponsored child abuse,” according to their letter, which asks for an immediate hearing.

The department’s approximately $50 billion budget makes it one of the US government’s biggest federal agencies, and Congress is supposed to police its spending and direction. It’s “standard practice to hold at least one oversight hearing for each session of Congress,” a congressional aide told Quartz, but the last time the House Judiciary Committee held a DHS oversight hearing was back in July 2015. Goodlatte was also its chair then. The last time the committee held a public hearing specifically about ICE’s immigration policies was back in 2012.

DHS secretary Kirstjen Nielsen was tentatively scheduled for a public hearing in front of the committee last month, but she canceled because she didn’t want to answer questions about family separations at the border, former and current DHS employees told Quartz. According to the letter, that hearing was supposed to be rescheduled “before the August recess,” which starts July 27.

The House’s lack of DHS oversight stands in sharp contrast to the Senate. In January, the Senate Judiciary committee grilled Nielsen about Trump administration immigration policy as part of its DHS oversight hearing. The Senate Intelligence Committee is also conducting a measured investigation into the 2016 election.