Washington DC - Lawmakers launched an investigation Thursday into antisemitism at three of the top US universities after their leaders quibbled over whether or not student protests calling for the genocide of Jews amounted to harassment.

The probe comes with the presidents of Harvard, the University of Pennsylvania, and the Massachusetts Institute of Technology facing a backlash over their testimony Tuesday on rising antisemitism on campus since the October 7 attack on Israel by Hamas militants.

The trio were pressed during a hearing in the House of Representatives on whether pro-Palestinian student activists calling for "Jewish genocide" violated their codes of conduct on harassment but all three equivocated, claiming it would depend on the context.

"After this week's pathetic and morally bankrupt testimony by university presidents when answering my questions, the Education and Workforce Committee is launching an official congressional investigation with the full force of subpoena power into Penn, MIT, Harvard, and others," Elise Stefanik, the fourth-ranking House Republican, said in a statement.

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"We will use our full congressional authority to hold these schools accountable for their failure on the global stage."

During the tense, five-hour hearing the presidents told Stefanik that calling for the genocide of Jews would only violate their schools' rules if it led to individuals being bullied.

Stefanik, who studied at Harvard, has called for the presidents to resign.

Harvard president Claudine Gay sought to clarify her comments Wednesday, arguing in a statement that critics were confusing "a right to free expression with the idea that Harvard will condone calls for violence against Jewish students."

Penn president Liz Magill said in a video statement that she should have been focused on the "irrefutable fact that a call for genocide of Jewish people is a call for some of the most terrible violence human beings can perpetrate."

The backlash to the hearing has been bipartisan, with the White House joining the condemnation.

"It's unbelievable that this needs to be said: calls for genocide are monstrous and antithetical to everything we represent as a country," a spokesman for President Joe Biden said in a statement.

Israel has been pressing for the destruction of Hamas over the October attack, when militants broke through Gaza's militarized border to kill around 1,200 people and seize hostages, 138 of whom remain captive, according to Israeli figures.

The bloodiest-ever war between Israel and Hamas is now in its third month, with the death toll in Gaza soaring above 17,000 according to the Hamas-run health ministry. The bloodshed has been accompanied by a rise in raucous student protests.

Virginia Foxx, the education committee's chairwoman, warned that other universities should expect to be caught up in the investigation.