A Davis Wright Tremaine partner has resigned from the firm after reports that the humanitarian organization on whose board he served, Mercy Corps, failed to adequately address serious sexual abuse allegations against its founder.

In an internal firm email sent Friday, Davis Wright Tremaine's managing partner, Jeffrey Gray, said Robert Newell, a litigation partner in the Seattle-based firm's Portland office, had resigned, effective immediately. Until last week, Newell was a board member for Mercy Corps, a major international nonprofit and a pro bono client of the law firm. The Oregonian reported earlier this month that the charity for decades covered up allegations that founder Ellsworth Culver, who died in 2005, sexually abused his daughter, Tania Culver Humphrey.

According to the newspaper, Newell, who has been actively involved with Mercy Corps for decades and has been a board member since the 1980s, conducted the initial review of Humphrey's allegations. After the Oregonian investigation was published, he resigned from the board, along with Mercy Corps' CEO and its senior legal counsel, Barnes Ellis, a former partner with Stoel Rives.

Newell could not immediately be reached for comment on Monday. In a statement to The Oregonian last week, following his resignation from Mercy Corps board, he said the board took Humphrey's claims "very seriously when they were brought to our attention," adding, "nothing changes the fact that no one should endure what she has described, especially not as a child at the hands of her father. … It is as troubling to me now as it was back then."

In his email to others at the firm Friday, Gray acknowledged Newell's involvement in reviewing Humphrey's allegations, noting he held a meeting with her in the firm's Portland office in the 1990s, although he said the firm did not have any related documents and he did not believe the firm played a role in the investigation.

"As many of you have seen, a horrific story came out this week about our pro bono client, Portland-based Mercy Corps, and allegations that its now deceased founder and CEO had sexually abused his daughter for years," the email said. "Since the story ran, our firm has spent countless hours reviewing and processing the details, which we were hearing for the first time, just as you were. Both personally and as a member of this firm, I was shocked and cannot begin to fathom what Ms. Humphrey went through. Nothing she described should ever happen to anyone."

The email continued: "While [Newell] has dedicated a significant part of his career and his life to pro bono service, primarily for Mercy Corps, in light of the circumstances, he informed us today that he is resigning from the firm."