The Commerce Department's inspector general, the official charged with investigating wrongdoing at the agency, announced his resignation in the midst of an investigation by a congressional committee into allegations of improper conduct.

Johnnie E. Frazier, who had served since 1999 as the agency's chief watchdog, said in a resignation letter obtained by The Associated Press that he would step down effective June 29.

In the letter, dated Thursday, he expressed "my disappointment and outright sadness at leaving Commerce at a time when my office and I are the subject of controversy."

The House Energy and Commerce Committee had launched an investigation into accusations against Frazier and members of his senior staff relating to travel fraud, contracting irregularities, wasteful expenditures, favoritism and retaliation against whistle-blowers.

In a statement, Committee Chairman John Dingell called Frazier's decision to step down a wise one but said that his panel's investigation was "far from over."

"We will continue to look into this matter to ensure the return of a well-run and functional inspector general's office at the Department of Commerce," Dingell, D-Mich., said.

Inspector generals are charged with uncovering evidence of waste, fraud and abuse at major federal agencies.

Rep. Bart Stupak, chairman of the Commerce panel's investigation subcommittee, said his panel had confirmed that Frazier and five of his subordinates had made a trip to Atlantic City to gamble while on official government travel to attend a conference.

"We are not done with this allegation nor the myriad other complaints we continue to receive about him and his office," Stupak, D-Mich., said in a statement.

Leaders of the committee last month had written a letter to Frazier and his deputies warning that the panel would not tolerate the "harassment and mistreatment" of subordinates in the office who were cooperating with the committee's investigation.

In his resignation letter, Frazier said that his office was "working diligently to provide the information to address these matters as quickly as possible."

Aides to Commerce Secretary Carlos Gutierrez did not immediately respond to requests for comment on Frazier's resignation.

Frazier, who was appointed inspector general at the Commerce Department in 1999 by President Clinton, has worked at the agency for 37 years.