WASHINGTON — President Obama, facing re-energized Republican adversaries and new questions about the administration’s conduct, on Monday dismissed a furor over the handling of last year’s attacks in Benghazi, Libya, as a political “sideshow” but joined a bipartisan chorus of outrage over disclosures that the Internal Revenue Service had singled out conservative groups for special scrutiny.

Mr. Obama called the I.R.S. reports “outrageous” and “contrary to our traditions,” adding his voice to those of Republicans and isolating the agency as the House scheduled a hearing on Friday in what is likely to be an extensive Congressional review of the agency’s actions.

“I’ve got no patience with it,” Mr. Obama said during a joint news conference at the White House with Prime Minister David Cameron of Britain. “I will not tolerate it. And we will make sure that we find out exactly what happened on this.”

Four months into his second term, the president was under increasing assault from Republicans who accused the administration of political bullying and a lack of transparency. Kathleen Sebelius, Mr. Obama’s secretary of health and human services, has drawn criticism in recent days for soliciting corporate donations to pay for the rollout next year of the new health care law.