Former US Ambassador Jon Huntsman blasted the University of Pennsylvania's response to antisemitism and is promising to halt his family's donations to the prestigious university.

The strong criticism from Huntsman, a 1987 graduate and former UPenn trustee, comes amid a growing backlash from donors and trustees. The Huntsman family has been such prominent supporters of UPenn that the Huntsman name is on the main Wharton School building.

The controversy began last month when a multiday event took place on campus at UPenn called the Palestine Writes Literature Festival. UPenn has acknowledged that event included speakers with a history of making antisemitic remarks, and UPenn leaders issued a statement ahead of the festival condemning antisemitism broadly, though not the festival specifically.

Powerful donors led by private equity billionaire Marc Rowan have argued UPenn leaders did not go far enough to condemn that event or speak out against antisemitism, particularly in the wake of Hamas' attack on Israel last weekend.

UPenn President Liz Magill, attempting to put out the fire, issued a statement Sunday admitting the school did not handle the situation as well as it could have.

But Huntsman was unmoved.

"The University's silence in the face of reprehensible and historic Hamas evil against the people of Israel (when the only response should be outright condemnation) is a new low," Huntsman wrote to Magill in a letter obtained by CNN. "Silence is antisemitism, and antisemitism is hate, the very thing higher ed was built to obviate."

The letter was first reported by student newspaper The Daily Pennsylvanian.

Huntsman, the former governor of Utah and US Ambassador to China, Singapore and Russia, is answering Rowan's call to donors to hit UPenn where it hurts most: donations.

"Consequently, Huntsman Foundation will close its checkbook on all future giving to Penn -- something that has been a source of enormous pride for now three generations of graduates," said Huntsman, who delivered the 2010 commencement speech at Penn.

In his letter, Huntsman called UPenn "deeply adrift" and decried leadership's "moral relativism" that he said "fueled the university's race to the bottom." He said inaction from UPenn's leaders forced him to speak out and suspend donations.

Following a three-hour emergency meeting of UPenn's Board of Trustees on Friday, trustee Vahan Gureghian resigned.

"Just as at so many other elite academic institutions, the Penn community has been failed by an embrace of antisemitism, a failure to stand for justice and complete negligence in the defense of our students' wellbeing," Gureghian wrote in his letter of resignation.

Magill, UPenn's president, is trying to quell the backlash and conceded the response to the Palestine Writes Literature Festival was inadequate.

"While we did communicate, we should have moved faster to share our position strongly and more broadly with the Penn community," Magill said in a statement Sunday.

The UPenn leader said she knows how "painful the presence of these speakers" on campus was for the Jewish community, especially during the holiest time of the Jewish year.

"The University did not, and emphatically does not, endorse these speakers or their views," Magill said.

"I want to leave no doubt about where I stand. I, and this University, are horrified by and condemn Hamas's terrorist assault on Israel and their violent atrocities against civilians," Magill said. "There is no justification — none — for these heinous attacks, which have consumed the region and are inciting violence in other parts of the world."

Magill also said the school has increased security and support for centers of Jewish life on and near campus and will continue "monitoring threats of violence."

Scott Bok, who chairs UPenn's board of trustees, said in a statement on Monday that dozens of current and former UPenn trustees gathered for a pair of virtual conversations in recent days to discuss the situation and hear from Magill.

"The unanimous sense of those gathered was that President Magill and her existing University leadership team are the right group to take the University forward," Bok said.