Ryan J. Reilly July 25, 2011, 9:50 AM

Rep. David Wu (D-OR) is resisting calls to resign following the revelation that he’s been accused of an unwanted sexual encounter with a young woman who is the daughter of a high school friend and campaign donor, but an aide says he has decided not to seek reelection.

But House Minority Leader Nancy Pelosi (D-CA) and Rep. Steve Israel (D-NY), chairman of the Democratic Congressional Campaign Committee, are calling for an immediate investigation into Wu by the House Ethics Committee.

“New allegations of unacceptable behavior by Congressman Wu are extremely serious and disturbing,” Israel said in a statement late Sunday. “I strongly agree with Leader Pelosi’s request that the House Ethics Committee use its authority to begin an immediate investigation.”

The Oregonian reported on the allegations against Wu on Friday. The newspaper reported that the young woman, who graduated from high school in 2010, left a “distraught” voice mail at Wu’s Portland office accusing him of an unwanted sexual encounter over Thanksgiving weekend.

The new development followed news earlier this year that Wu had suffered from mental health issues in recent years and sent a photo of himself dressed in a tiger costume to staffers. Six staffers left his campaign following his reelection in November. Staffers had tried to intervene with Wu after a series of questionable actions: using his position to break airport security rules, making an aggressive speech, and sending strange emails to his staffers written in the voice of his children.

Politico reported on more strange behavior from Wu: he reportedly accused congressional staffers of stealing a lighter and demanded to be let onto the floor during the House’s opening prayer.

David Wu, House Democrats, House Ethics Committee