Planned Parenthood president Cecile Richards on Tuesday for the first time directly addressed members of Congress about undercover videos purporting to show that the women’s health organization illegally sells fetal tissue for profit, telling members of the House Oversight committee that the allegations are “offensive and categorically untrue.”

At a hearing centering on whether federal funding should continue for the group, Richards forcefully defended her organization, calling it a critical source for cancer screenings, testing and treatment for sexually transmitted diseases, contraception care and other services for millions of women, particularly those who are low-income.

“For many American women, Planned Parenthood is the only health-care provider they will see this year,” she said during her opening testimony. “It is impossible for our patients to understand why Congress is once again threatening their ability to go to the health-care provider of their choice.”

But the hearing quickly turned into a grilling, with Republican lawmakers aggressively questioning Richards on everything from her annual salary to the support of Democratic candidates provided by the group’s political action committee; often delivering rapid-fire questions that left little time for her to respond.

The hearing came as congressional leaders approached an agreement that would keep the government funded through Dec. 11, likely averting a shutdown that had loomed this week arising from a dispute over whether Planned Parenthood should continue to receive federal dollars.

The organization and its affiliates receive more than $500 million in state and federal funds, primarily through grants and Medicaid reimbursements.

Congressional Republicans are moving ahead with a plan to go after the group’s funding outside of the annual spending bills. This week, House committees announced they will begin assembling a so-called budget reconciliation bill that would cut off funding for the group. Legislation moved through the reconciliation process cannot be filibustered in the Senate, meaning Republicans could force President Obama to veto the bill.

Defunding Planned Parenthood is a perennial concern for conservative Republicans, but the effort gained urgency this summer after a little-known anti-abortion organization called the Center for Medical Progress released video obtained covertly over the course of 30 months that purported to show that Planned Parenthood affiliates illegally sell fetal parts to research companies for a profit.

Federal law allows abortion clinics to recover the cost of providing fetal tissue leftover from abortions to researchers, but bars them from profiting.

At the hearing, Richards reiterated her support for the organization’s fetal tissue donation program while downplaying its role, saying that less than 1 percent of the group’s affiliates participate. The few affiliates that participate in fetal tissue donation provide it as a service to women, she said.

Rep. Jason Chaffetz (R-Utah), the chairman, interrogated Richards about her $520,000 annual salary, her organization’s travel budget and overseas spending, and the work of the group’s advocacy arm, Planned Parenthood Action Fund.

Richards said that the federal money that the organization receives, through grants and Medicaid reimbursements, is used solely for the health services and that the Action Fund is a separate corporation. But Chaffetz raised an issue that has long bothered conservatives — that the federal support may free up money for Planned Parenthood to fund other activities.

“It’s the co-mingling [of the funds] that bothers us,” he said.

Rep. Elijah Cummings (D-Md.), ranking member of the committee, accused Republicans of singling out Planned Parenthood because of ideological opposition to abortion. He rattled off a list of private companies, such as banks, found to have committed illegal acts and whose executives make millions of dollars.

“Ms. Richards, do you know if House Republicans made any effort to strip the banks of their federal support that I just talked about?”

Richards responded that she did not.

Supporters of Planned Parenthood aimed to make a significant show of support Tuesday, which they declared “National Pink Out Day.” Planned Parenthood officials expected about 300 events across the country and asked supporters to alter their social media profiles to show support for the group.

A group of about 42 Planned Parenthood supporters dressed in pink T-shirts with the Planned Parenthood logo had turned up at the hearing in hopes of showing their support for Richards. But the activists say they were blocked from the room, despite having shown up at 8:30 a.m., an hour and a half before the hearing was to begin.

Emily Hein, a George Washington University student and Planned Parenthood volunteer, said her group was within about 15 people from the front of the line, which wrapped around the hallway. At some point amid a relatively chaotic scene, she said, staff from Republican leadership shuffled the pink-clad activists to another area.

Staff then permitted a row of people in suits and others in “Defund Planned Parenthood” T-shirts into the room before closing the door, she said.

“They offered us an overflow room, which is upstairs,” Hein said, explaining that audio from the hearing is being pumped into that room. “Most of our volunteers went up there. But there are some of us still outside in line because we would like to be a part of the hearing.”

MJ Henshaw, a spokeswoman for the House Oversight committee, said the issue was a matter of space in the hearing room.

“This is a highly attended hearing and — just like other high profile hearings at the Committee — unfortunately the main hearing room can not accommodate all those who wish to attend,” Henshaw said in an e-mail. “For those attendees, we provide an overflow room to view the hearing.”