WASHINGTON (Reuters) - House of Representatives Democratic leader Nancy Pelosi said she will seek an ethics investigation Monday into sexual misconduct allegations against Representative David Wu.

Pelosi called for the investigation after reported accusations that the Oregon Democrat had an unwanted sexual encounter with the teen-aged daughter of a campaign donor.

"With deep disappointment and sadness about this situation, I hope that the Ethics Committee will take up this matter," Pelosi said in a statement Sunday.

Pelosi said she would send a formal request to the House Ethics Committee on Monday.

The chairman of the Democratic Congressional Campaign Committee, Representative Steve Israel of New York, backed Pelosi's decision.

"New allegations of unacceptable behavior by Congressman Wu are extremely serious and disturbing," Israel said.

The new allegations follow other behavior problems for Wu.

He announced in February that he was undergoing psychiatric treatment after his staff complained about his erratic behavior in the run up to the November 2010 Congressional elections.

They said Wu had behaved strangely at meetings and had e-mailed pictures of himself wearing a tiger suit to staff. Several key staff members resigned following the election.

Wu, who represents the Portland area, is in his seventh two-year term in the House. Two Democrats have already announced they will seek Wu's seat in the 2012 congressional election.

Politico quoted an unidentified Wu adviser late Sunday night as saying that Wu would not resign.

Former Representative Anthony Weiner, a New York Democrat, resigned in June over an Internet sex scandal.

(Reporting by JoAnne Allen; editing by Doina Chiacu)

Source: Reuters US Online Report Politics News