Thousands of academics have signed an open letter calling for a US boycott following the announcement of President Donald Trump’s travel ban.

More than 4,500 scholars from across Europe, Asia, Australia, Canada, Latin America, Africa and the Middle East have signed the petition, pledging to boycott international conferences held in the country while the controversial new restrictions – referred to as a “Muslim ban” – are in place.

Mr Trump’s new policy, brought in on Friday, blocks refugees from entering the country for a 120-day period. There is an indefinite ban on refugees from Syria and a 90-day ban on citizens from Iraq, Iran, Somalia, Sudan, Syria and Yemen.

The ban has been met with condemnation and prompted mass protests in major cities around the world.

Among the groups affected are students and academics who study and teach in US universities, a number of whom are said to have cancelled upcoming trips as a result.

Dr Nadine el-Enany, a University of London lecturer who was involved in creating the petition, told Middle East Eye the purpose of the letter was to “be clear about [academics’] opposition to the ban” and “not carry on with ‘business as usual at a time of emergency”.

Protestors rally at JFK Airport against Muslim immigration ban Show all 20 1 /20 Protestors rally at JFK Airport against Muslim immigration ban Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-1 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-2 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-3 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-4 SAN FRANCISCO, CA - JANUARY 28: Demonstrators hold signs during a rally against a ban on Muslim immigration at San Francisco International Airport on January 28, 2017 in San Francisco, California. President Donald Trump signed an executive order Friday that suspends entry of all refugees for 120 days, indefinitely suspends the entries of all Syrian refugees, as well as barring entries from seven predominantly Muslim countries from entering for 90 days. Stephen Lam/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-5 A crowd of protesters gathers outside of the Brooklyn Federal Courthouse as a judge hears a challenge against President Donald Trump's executive ban on immigration from several Muslim countries, on January 28, 2017 in Brooklyn. The judge issued an emergency stay on part of Trump's executive order, ruling that sending refugees stopped at U.S. airports back to their countries would be harmful. Yana Paskova/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-6 Protestors rally during a demonstration against the new immigration ban issued by President Donald Trump at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-7 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the new immigration ban issued by President Donald Trump at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-8 Protestors rally during a demonstration against the new immigration ban issued by President Donald Trump at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-9 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. (Photo by Stephanie Keith/Getty Images) Getty Images Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-10 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. (Photo by Stephanie Keith/Getty Images) Getty Images Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-11 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-12 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-13 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-14 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-15 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-16 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-17 NEW YORK, NY - JANUARY 28: Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-18 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-19 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-20 Passengers wait in line to check in at the American Airlines terminal at JFK International Airport August 10, 2006 in the Queens borough of New York City. British authorities arrested 21 people and halted a anallegedly terrorist plot to use liquid explosives concealed in carry-on luggage to blow up airliners traveling between Britain and the U.S. Homeland Security chief Michael Chertoff said that the plot appeared to be directed at U.S. carriers flying out of Heathrow. such as United Airlines, American Airlines, Continental Airlines. Stephen Chernin/Getty

“It is an attempt to draw necessary attention to the urgency of the 'Muslim ban' and to generate conversation on the far-reaching consequences,” she said, “not only for those who are nationals from the seven countries identified by Trump's executive order, but also for many others who are not from these countries but who are nonetheless being detained and harassed at the border”.

Dr el-Enany, who lectures at Birkbeck, criticised some US academic unions for failing to condemn the President’s executive order outright.

The open letter states: “We the undersigned take action in solidarity with those affected by Trump’s Executive Order by pledging not to attend international conferences in the US while the ban persists.

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“We question the intellectual integrity of these spaces and the dialogues they are designed to encourage while Muslim colleagues are explicitly excluded from them.”

The proposed boycott has divided opinion, however, with some suggesting it could hinder US universities and that the academics’ frustrations are unlikely to register with US government authorities.

Marina Costin Fuser, PhD candidate in film studies at the University of Sussex, said “American universities” should not be “our target”.

She told Times Higher Education: “Let's be supportive of US universities at times like this. Universities have the potential to encourage critical ideas and organise resistance.

“I don't think Trump cares that much about higher education to actually feel threatened by this conference ban...unless applied hard scientists join in, we'll be boycotting ourselves – that is, departments that lean to the left, such as arts and humanities.”

This week Harvard University President Drew Faust also publicly condemned Mr Trump's executive order, observing that almost half of the world-leading institution’s deans are immigrants from countries including Iran.