WASHINGTON  Housing secretary Alphonso R. Jackson resigned on Monday, saying that he needed to devote more time to his family. The announcement came as federal authorities were investigating whether he had given lucrative housing contracts in the Virgin Islands and New Orleans to friends.

His resignation, effective April 18, also comes as the Bush administration is increasingly relying on the department’s Federal Housing Administration to help stanch the widening foreclosures.

In recent weeks, Mr. Jackson had faced mounting pressure to leave his post. The FBI has interviewed several of his employees, and two senior Democratic senators called on him to resign, saying the allegations of wrongdoing had undermined his leadership. Lawmakers have also raised concerns about accusations that Mr. Jackson had threatened to withdraw federal aid from the Philadelphia Housing Authority after its president refused to turn over a $2 million property to a politically connected developer.

Mr. Jackson, who assumed his post as secretary in 2004, did not address those allegations during his brief statement in the 10th floor briefing room of the U.S. Department of Housing and Urban Development.