The only black member of Harvard’s seven-person governing board has resigned his post to express his disaffection with the university’s often-embattled president, Lawrence Summers.

The resigning board member, Conrad Harper, a Midtown Manhattan resident and former civil litigator at Simpson, Thacher & Bartlett, told The New York Sun yesterday: “The reason for my resignation is that I can no longer support President Summers.”

The resignation threatens to revive the controversy that erupted after Mr. Summers suggested at an academic conference in January that innate differences between the two sexes could partially explain the paltry representation of women in the upper echelons of the science and engineering fields. In March, professors from one of Harvard’s 10 divisions, the Faculty of Arts and Sciences, approved a resolution expressing a “lack of confidence” in Mr. Summers’s leadership.

Mr. Summers has also sparred with members of Harvard’s African-American studies department, and one of the school’s most prominent black professors, Cornel West, bolted from Harvard and joined the Princeton faculty in 2002. That move came after Mr. Summers, in a private meeting, suggested that Mr. West, who had recorded a rap album and joined the Reverend Alford Sharpton’s presidential campaign, was neglecting his traditional academic duties.

Mr. Harper said he wrote a letter to Mr. Summers on July 14 setting forth his reasons for resigning, and he said “that letter should speak for itself.” While he declined to divulge the details of the letter, he said: “I have no objection to Harvard releasing it.”

But Harvard’s vice president for government, community, and public affairs, Alan Stone, told the Sun that the university would not release Mr. Harper’s letter. “We regard corporation communications as confidential,” Mr. Stone said.

One of Mr. Summers’s most vehement faculty critics, Harvard anthropologist J. Lorand Matory, said Harvard should release Mr. Harper’s letter of resignation. “It is apparently left to Mr. Summers to see if he has the courage to expose criticisms made of him and to respond to those criticisms.”

Mr. Matory, who is black, said he has “no doubt that Mr. Harper’s concerns are related to Mr. Summers’s rather immoral and unethical postures toward women, toward the Palestinians, and toward African-Americans.” Mr. Matory’s reference to Palestinians is an apparent allusion to Mr. Summers’s remarks in September 2002, when he suggested that a push from some faculty members who wanted Harvard to cut financial ties to Israeli firms was “anti-Semitic in its effect if not its intent.”

A Harvard economist and Summers ally, Richard Zeckhauser, said Mr. Harper’s resignation did not reflect any new groundswell of opposition to the school’s president. “The faculty that I know are quite supportive of President Summers, and I think even some of those people who were initially unsupportive of him are now supporting him,” Mr. Zeckhauser said. He noted that several professors who had suggested they might leave Harvard in the aftermath of Mr. Summers’s controversial January remarks, including economist Caroline Hoxby, have not done so.

Mr. Harper became the first black person to sit on the school’s governing board in 2000, and he served on the presidential search committee that selected Mr. Summers in 2001. The Harvard Crimson reported that during the presidential search, Mr. Harper was notably critical of Mr. Summers’s brusque manner.

An avid fan of woodwind music who also sits on the board of the Metropolitan Museum of Art, Mr. Harper said leaving his Harvard post would give him more time to practice his recorder and to pursue his travel plans, which include a trip to China this fall.

Mr. Summers issued a statement yesterday that made no reference to his apparent spat with Mr. Harper. “Conrad Harper’s candid and insightful counsel on wide range of important matters has strongly benefited the University,” Mr. Summers said. “I am grateful to him, both personally and on Harvard’s behalf, for his devoted service and for the many contributions he has made to the work of the Corporation.”