Updated: 11:46 p.m.

House Minority Leader Nancy Pelosi (D-Calif.) called Sunday night for an ethics investigation into allegations that embattled Rep. David Wu (D-Ore.) forced an “unwanted sexual encounter” with a young woman.

Pelosi’s statement came shortly after Politico first reported that Wu would not seek an eighth term next year, which a Democratic source confirmed, adding that pressure is building for his resignation.

“With deep disappointment and sadness about this situation, I hope that the Ethics Committee will take up this matter,” Pelosi said. “I will send a letter to the Ethics Committee [Monday] asking them to formally initiate a review of this matter.” Democratic Congressional Campaign Committee Chairman Steve Israel (N.Y.) supported the Minority Leader’s request in a separate statement.

Wu came under fire Friday after the Oregonian reported that “a distraught young woman” called Wu’s Portland office this spring, “accusing him of an unwanted sexual encounter.”

In a brief statement in response to the Oregonian report, Wu said only, “This is very serious, and I have absolutely no desire to bring unwanted publicity, attention or stress to a young woman and her family.”

Over the weekend, Wu spoke with Pelosi, Israel and House Democratic Caucus Chairman John Larson (Conn.).

Friday’s report is the latest in a series of unflattering stories about erratic behavior that have put Wu on the defensive in recent months and stretch at least as far back to his 2010 re-election bid.

In February, Wu said that sending his staffers photos of himself in a tiger costume was “inappropriate.” The Congressman said he is getting mental health treatment and acknowledged he is taking medication. At the time, Congressional leaders showed token support for Wu publicly and did not call on him to resign. Asked about Wu’s behavior at a news conference in March, House Minority Whip Steny Hoyer (D-Md.) said that it was “premature” for Wu to step down from office and noted that he was dispatching his deputy chief of staff “to make sure that he gets help.”

Wu was already facing a primary challenge against Oregon Labor Commissioner Brad Avakian and state Rep. Brad Witt, and redistricting could have further complicated the Congressman’s re-election efforts in 2012.

Avakian used Sunday’s developments to repeat his call for Wu to resign.

“David Wu’s reported plan to remain in office but not seek reelection puts David Wu first and his constituents last,” he said in a statement. “It ensures the voters of the First Congressional District will be without effective representation for the next 17 months as Wu is subject to a House Ethics Committee investigation and faces a complete loss of authority and influence within the Democratic caucus. … For the sake of our community and this young woman and her family, as well as his own family, David Wu should do the right thing and step aside now.”