WASHINGTON - Eric Lander, President Joe Biden's top science adviser, resigned Monday night after he acknowledged mistreating his subordinates and apologized for demeaning them, a pattern of behavior that put him at odds with one of Biden's earliest promises - to run an administration marked by respect and professionalism. 

An internal review by the White House found credible evidence that Lander, director of the Office of Science and Technology Policy, bullied staff in violation of the White House's "safe and respectful workplace policy," which was intended in part to draw a contrast with the Trump administration.

Lander's resignation came after the White House struggled throughout the day to explain why he had not quit or been fired, and how that squared with a pledge Biden made on his first day in office. On that day, he told staffers at swearing-in ceremony, "If you are ever working with me and I hear you treat another colleague with disrespect, talk down to someone, I promise you I will fire you on the spot. On the spot - no if, ands or buts."

In a letter to Biden on Monday night, Lander said he was resigning effective no later than Feb. 18 to "to permit an orderly transfer."

"I am devastated that I caused hurt to past and present colleagues by the way in which I have spoken to them," he wrote. "It is clear that things I said, and the way I said them, crossed the line at times into being disrespectful and demeaning, to both men and women. That was never my intention. Nonetheless, it is my fault and my responsibility. I will take this lesson forward. I believe it is not possible to continue effectively in my role, and the work of this office is far too important to be hindered."

White House press secretary Jen Psaki said in a statement that Biden accepted Lander's resignation "with gratitude for his work at OSTP on the pandemic, the cancer moonshot, climate change, and other key priorities." She added, "He knows that Dr. Lander will continue to make important contributions to the scientific community in the years ahead."

Lander had been overseeing two initiatives of enormous importance to Biden. One is a reboot of the cancer "moonshot," which Biden led as vice president during the Obama administration after his 46-year-old son, Beau, died of brain cancer in 2015.

The other is the proposed creation of an advanced research agency to propel breakthrough medical treatments for cancer, diabetes, Alzheimer's and other life-threatening diseases. The House Energy and Commerce subcommittee on health, chaired by Rep. Anna Eshoo, D-Calif., is scheduled to hold a hearing Tuesday to discuss the proposal; Lander had been scheduled to testify, but his appearance was canceled Monday.

Inside the White House, many staffers were irate that Lander initially appeared to be keeping his job, arguing that there is a double standard for men and those in position of power. In conversations with staffers on Monday, all of whom spoke on the condition of anonymity because they were not authorized to speak to the press, they said that Biden had set a clear standard for workplace behavior and that he should fire Lander.

Female staffers in particular raised concerns about Lander's pattern of belittling women at the White House, complaints that were corroborated by the internal White House investigation. Some noted Biden's close personal relationship with Lander, who served on the board of the Biden Cancer Initiative, the nonprofit Biden started after his term as vice president ended.

In a note to staff on Friday, obtained by The Washington Post, Lander acknowledged that he did not "set a respectful tone for our community."

"I have spoken to colleagues within OSTP in a disrespectful or demeaning way," he wrote. "It is never acceptable for me to speak that way. I am deeply sorry for my conduct. I especially want to apologize to those of you who I treated poorly, or were present at the time."

Lander said OSTP will schedule forums "to check in with staff on how we are doing in creating and upholding a safe and respectful workplace."

The investigation, which was first reported by Politico, was sparked by a complaint filed last year by Rachel Wallace, who was then serving as OSTP's general counsel, and found that multiple women had complained about negative interactions with Lander.

Wallace, a civil servant, has also accused Lander of retaliating against her by demoting her to deputy counsel. The White House investigation did not find credible evidence of gender-based discrimination and deemed Wallace's reassignment appropriate.

Wallace referred comment to her lawyer, David Seide of the Government Accountability Project.

"Dr. Lander's conduct is disturbing," Seide said. "Rachel was wrongly retaliated against. We will have more to say about this shortly."

Before Biden brought him into the administration, Lander was the founding director of the Broad Institute, a genetics research center based in Cambridge, Mass. A leading researcher of the human genome, he also helped pioneer the use of DNA in forensic science.

Biden tapped Lander in part to signal a course change from former President Donald Trump, who regularly criticized and demeaned the scientists in his administration struggling to deal with the pandemic. To further emphasize the importance of science, Biden elevated the post of OSTP to a Cabinet-level position.

Lander is a gifted communicator and fundraiser - philanthropic mega-donations from billionaires were fundamental to the Broad Institute, which has grown into a genetics powerhouse fueled by funding from the federal government, philanthropy and industry. In January 2021, shortly before Biden was inaugurated, he wrote Lander a public letter asking for advice on pressing questions, including what could be learned from the coronavirus pandemic about improving public health.

Despite Lander's influential position in the scientific world, his nomination drew immediate criticism from some in the scientific community who raised concerns about his treatment of other scientists, particularly women and people of color. Lander faced tough questions at his confirmation hearing from Democratic and Republican senators, who raised concerns about his past actions, and was eventually the last member of Biden's Cabinet to be confirmed in May.

In 2016, Lander authored a controversial history of CRISPR, a powerful gene-editing technology, that downplayed the contributions of the two female scientists, Jennifer Doudna and Emmanuelle Charpentier, who have since been awarded the Nobel Prize for their work. During his Senate confirmation hearing in 2021, Lander acknowledged he had "understated" their contribution and called that a "mistake" he regretted.

In 2018, he faced criticism for giving a birthday toast to James Watson, the Nobel Prize winner whose racist and sexist comments have marred his scientific reputation. Lander apologized for toasting Watson.

Before Lander's resignation, Republicans suggested Biden was acting hypocritically by not firing him.

"Bullying or demeaning subordinates is never acceptable," Sen. Roger Wicker, R-Miss., the top Republican on the Senate Commerce Committee. "Dr. Lander's apology to his OSTP staff indicates that the allegations are credible ... If Lander's behavior was disrespectful, then he should not continue to serve in the administration."

On Monday, the American Association for the Advancement of Science said it was disinviting Lander, who was scheduled to speak at its annual meeting next week.

Emily Pinckney, the executive director of 500 Women Scientists, said her group was not surprised by the findings of the investigation because of Lander's past behavior. Pinckney's organization opposed Lander's selection, writing in Scientific American in January 2021 that Biden's choice ensured "the glass ceiling in American science remains intact."

"We're really happy that there is a scientific adviser role in the Cabinet," she said. "There is always a long list of folks to choose from and we feel it was a misstep to choose Lander ... . It's not because his work isn't good, but because he is known for being a bully."

Biden appeared publicly with Lander last week when the president unveiled the blueprint for the cancer moonshot, a project aiming to bolster prevention, screening and research, with the goal of reducing the death rate from cancer by 50% during the next 25 years.

Biden said Lander and his office will "chart the path for the cancer moonshot for 2022 and beyond." For now, there is no proposal on how to fund the plan, and some cancer advocates expressed alarm Monday that the effort could founder if Lander leaves the administration.

The Washington Post's Laurie McGinley, Carolyn Johnson, Sarah Kaplan and Mariana Alfaro contributed to this report.