Lecturers should not compliment a foreign student's English because it is a potentially racist "microaggression", leading British universities say.
Saying "you speak English so well" or "you're so articulate" to an ethnic minority student carries an assumption white people are more intelligent, according to Imperial College London, as it issues staff with a list of phrases to avoid on campus.
Microaggressions are "subtle, invisible and insidious" remarks that create an "internal conflict" for minorities who experience them, the university says in diversity training manuals, likening the impact to "death by a thousand cuts".
Scholars are told it is "denigrating cultural values/communication styles" to tell an East Asian person to "speak up more" or to tell a black person "why do you have to be so loud? Just calm down".
Campus security guards are told not to ask a black member of staff if they are lost because this carries "assumptions of criminality".
Imperial's guide adds that uttering the phrase "I'm not racist. I have several black friends" is denying minorities' experience of bias.
Staff should not say "I believe the most qualified person should get the job. We need excellence!" because this perpetuates the "myth of meritocracy" that BAME people are not disadvantaged.
Meanwhile, Edinburgh University has told staff and students not to say "your English is really good" to anyone who is black, Asian British, Nigerian or American because this is a "microinsult".
This means a subtle snub, conveying insult to the recipient and denying bias.
Plans to tackle 'rising intolerance'
It comes as the government unveiled new free speech laws in the Queen's Speech to tackle "rising intolerance" on campuses.
In a crackdown on cancel culture, students and academics will be able to sue for compensation through the courts if they feel unfairly silenced.
Toby Young, general secretary of the Free Speech Union which has dealt with 100 cases of campus censorship in the past year, said protections from "over-reaching diversitycrats" trying to police speech and thought are urgently needed.
"Universities have no business telling their academic staff what they can and can't praise about their students' work," he said.
"Surely, the way to create a welcoming environment for BAME students at a university is to assure them they will be treated in exactly the same way as every other student? To hold BAME students to a lower standard than white students is incredibly patronising.
"These misguided woke initiatives, which undermine academics' autonomy and professional integrity, is exactly why we need more protection for free speech on campus."
Imperial's microaggressions guide and video, produced by the Faculty of Engineering, urges staff to think about how they make others feel in all interactions, and ensure they acknowledge race, age and gender.
Edinburgh University, which declined to comment, also urges students in diversity training not to engage in avoidant behaviour around BAME people or say they are being oversensitive if they feel offended, as these are "microinvalidations".
A spokesman for Imperial College London said: "A video on the experiences of BAME colleagues does not 'threaten free speech', and we would reject any efforts to shut down these important discussions."