The first black member of Harvard’s governing board, Conrad Harper, resigned his post last month because he “could not and cannot support a raise” in the salary of the school’s president, Lawrence Summers.

In a stinging three-page letter to Mr. Summers that was released by the university yesterday, Mr. Harper, a former State Department official and civil litigator, called on the school’s embattled president to step down.

Mr. Harper’s letter marks the most potent challenge to Mr. Summers’s leadership since Harvard’s Faculty of Arts and Sciences, one of the university’s 10 divisions, in March approved a resolution expressing a “lack of confidence” in Mr. Summers.

The immediate impetus for Mr. Harper’s departure was the corporation’s decision last month to award Mr. Summers a 3% salary raise. The president will receive $580,000 for the current fiscal year, which began July 1. That marks the smallest year-to-year increase of Mr. Summers’s tenure, according to the university’s vice president for government, community, and public affairs, Alan Stone.

However, 3% was still too much for Mr. Harper, who wrote to Mr. Summers that, “In my judgment, your 2004-2005 conduct, implicating, as it does, profound issues of temperament and judgment, merits no increase whatever.”

A survey by the Chronicle of Higher Education last year found Mr. Summers’s salary ranked sixth out of eight Ivy League presidents.

While Mr. Summers’s relations with faculty members have been rocky ever since the former treasury secretary took office as president of the nation’s oldest university in September 2001, tensions escalated this past January after he suggested that innate differences between the sexes could partially explain the paltry representation of women in the upper ranks of the science and engineering fields.

Mr. Harper also said he was irked by Mr. Summers’s speech to an academic conference last September in which the president suggested the decimation of North America’s indigenous population “was in many ways a coincidence.” Although the chair of the Native American studies department at Stanford, C. Matthew Snipps, said Mr. Summers’s remarks were “factually correct,” the president’s speech offended several American Indian scholars in attendance.

Mr. Summers publicly apologized for his remarks on women and American Indians, but in both cases, the president’s mea culpa did not mollify Mr. Harper. “Your statements demeaned those who are underrepresented at the top levels of major research universities,” he wrote in his letter.

As Mr. Summers weathered criticism on campus and in the national press earlier this year, the president always appeared to have the support of the Harvard Corporation, the school’s powerful, seven-member governing body. However, Mr. Harper said he first called for Mr. Summers’s resignation – privately – on March 17, two days after the no-confidence vote.

The New York Sun reported yesterday that a broad-based group of faculty members was preparing a statement – slated to be released yesterday afternoon – that would have called on the school to release Mr. Harper’s letter of resignation. University officials had previously insisted that “corporation communications are confidential.”

The outgoing chairman of the school’s African American studies department, Henry Louis Gates Jr., told the Sun yesterday: “We feel that we have won without firing a shot.

“Those of us concerned with Conrad Harper’s honor and the integrity of the university are pleased that the university has reached this decision,” said Mr. Gates, a past winner of the MacArthur Foundation’s “genius grant.”

Mr. Summers sent a brief but gracious letter to Mr. Harper yesterday, in which the president wrote: “I deeply regret your decision to resign from the Harvard Corporation but recognize that you have taken this step only after careful consideration. You have contributed significantly to the work of the University, and your advice and counsel will be missed.”

The most senior member of the corporation, James Houghton, the former chief executive of the glass-making giant Corning, expressed his continued support for Mr. Summers in a statement yesterday.

Mr. Houghton issued the statement on behalf of four other Harvard Corporation members: the former president of Duke University, Nannerl Keohane; the former Congressional Budget Office chief, Robert Reischauer; a hedge fund manager, James Rothenberg, and Robert Rubin, a former Treasury secretary.