Washington (CNN) -- House Democratic leader Nancy Pelosi called Sunday for an ethics investigation of Congressman David Wu of Oregon, who has resisted calls to resign following a news report alleging he made sexual advances toward the daughter of a longtime campaign donor.
The allegations against Wu, a seven-term Democratic congressman, were published Friday by The Oregonian newspaper in Portland.
"With deep disappointment and sadness about this situation, I hope that the Ethics Committee will take up this matter. I will send a letter to the Ethics Committee tomorrow asking them to formally initiate a review of this matter," Pelosi said in a written statement.
The newspaper report states a young woman called Wu's Portland office this spring, accusing Wu of an unwanted sexual encounter.
"This is very serious, and I have absolutely no desire to bring unwanted publicity, attention or stress to a young woman and her family," Wu said in a written statement given to CNN.
The woman, according to The Oregonian, is the daughter of a longtime friend and campaign donor. The woman apparently did not contact police, the newspaper reported.
Calls for Wu's resignation began shortly after the newspaper made the story public.
"New allegations of unacceptable behavior by Congressman Wu are extremely serious and disturbing," Rep. Steve Israel, chairman of the Democratic Congressional Campaign Committee, said in a written statement.
"I strongly agree with Leader Pelosi's request that the House Ethics Committee use its authority to begin an immediate investigation."
CNN's Deirdre Walsh contributed to this report.