NRC Chairman Gregory Jaczko said in a written statement that it was the right time to step down, adding that he hoped his successor would keep a strong focus on safety.
Jaczko, 41, did not mention the bullying allegations in his statement, but he has been dogged by criticism that his unyielding style had created a chilled working environment at the nuclear commission, which oversees safety at the nation's 104 commercial nuclear reactors.
The four other commissioners on the five-member panel had accused Jaczko of intimidation and bullying and said women at the agency felt especially threatened.
The commissioners — two Democrats and two Republicans — sent a letter to the White House in October expressing "grave concern" about Jaczko' s actions, which they said were "causing serious damage" to the commission and could adversely affect safety at the nation's nuclear power plants.
White House spokesman Clark Stevens said President Barack Obama appreciates Jaczko's service and efforts to further the mission of the Nuclear Regulatory Commission.
"A strong and effective NRC is crucial to protecting public health and safety, promoting defense and security, and protecting the environment, and we intend to nominate a new chairman soon," Stevens said.
Jaczko, who has denied any wrongdoing, was the agency's public face during its response last year to an earthquake and tsunami that triggered nuclear meltdowns at the Fukushima Dai-ichi nuclear plant in Japan. He also took responsibility for recommending that U.S. citizens living in Japan evacuate an area larger than what U.S. communities near nuclear facilities prepare for, a decision that lawmakers and the NRC's advisory board questioned.
An inspector general's report released last summer said Jaczko had intimidated staff members who disagreed with him and withheld information from members of the commission to manipulate their decisions on critical votes.
Jaczko, a former aide to Senate Majority Leader Harry Reid of Nevada, was appointed by Obama in 2009 to lead the independent agency. Since then, he has made a series of decisions to delay or halt work on a proposed nuclear waste dump at Nevada's Yucca Mountain, a project Obama promised to kill in his 2008 campaign for the White House.
Jaczko's actions have been criticized by House Republicans, by his own scientific staff and by the NRC's inspector general. The IG report found that Jaczko acted within his authority and broke no laws. But it also concluded that to get his way on the issue he failed to be forthcoming with other commissioners.
Reid, the leading opponent of the Yucca Mountain nuclear waste site, praised Jaczko's service to the commission on Monday.
"He dedicated his tenure to improving the safety of nuclear energy, and his leadership during the Fukushima nuclear crisis protected millions of Americans," Reid said in a statement.
Jaczko had served on the commission since 2005. His term was due to expire next year.
___
Henry reported from Atlanta. Associated Press writer Dina Cappiello in Washington contributed to this story.