Harvard has banned its professors from sexual or romantic relationships with students in the latest move by a major US college to deal with controversies about behaviour on campus.
"Undergraduates come to college to learn from us," said Alison Johnson, a history professor who headed the Harvard panel that drew up the new rules.
"We're not here to have sexual or romantic relationships with them."
Some US universities, including Harvard, already ban relationships between faculty members and their students.
But the Ivy League college has now extended that policy to cover any sexual or romantic liaisons between an academic and an undergraduate, even if there is no teaching link between them.
Many students and parents believed that a campus-wide prohibition on such relationships was already in place to prevent professors exploiting their status or popularity for sexual or romantic ends.
But at many colleges, relationships have so far been discouraged but not explicitly prohibited. Yale University and the University of Connecticut have already introduced similar bans and other colleges are now expected to follow suit.
A powerful national professors' group said it did not favour a blanket ban on relationships between consenting adults as that would "throw the whole thing into darkness by prohibiting it".
Harvard began its review after the federal department of education opened an investigation into the handling of accusations of sexual assault and harassment at dozens of colleges, including the elite Massachusetts institution.
The changes were laid down as part of new guidelines on sexual discrimination and harassment. The policy also bans some other junior faculty members, such as graduate students who in turn oversee undergraduates, from relationships.
Although the American Association of University Professors has said relationships between professors and students are "fraught with the potential for exploitation", it does not recommend a formal ban. "These relationships are going to occur on campus and you must put as many ethical checks on them as possible, but a blanket prohibition doesn't seem appropriate," Anita Levy, a programme officer with the association, told Bloomberg News.