The University of Exeter banned students from staging a street theatre performance called Mock Checkpoint. Photograph: Christopher Thomond

Universities have been accused of undermining freedom of speech on campus after cancelling events organised by students as part of an annual pro-Palestinian event called Israel Apartheid Week (IAW).

The University of Exeter and the University of Central Lancashire (UCLan) intervened to cancel student-run events this week, aimed at raising awareness about Palestinian human rights. An event called Quad Under Occupation at University College London was also cancelled because organisers failed to get the necessary approval in time.

At Exeter, the Friends of Palestine Society were furious after the university banned students from staging a street theatre performance called Mock Checkpoint, in which some participants were to dress up as Israeli soldiers while others performed the roles of Palestinians.

The event, which had been approved by the students guild the universitys student union as part of an international week of talks and activities on campuses around the world, was banned for safety and security reasons less than 48 hours before it was due to take place on Monday. An appeal against the decision was refused.

Almost 250 academics, including 100 professors, have signed a letter condemning attempts to silence campus discussion about Israel and its treatment of Palestinians.

The letter criticises the universities minister, Jo Johnson, who recently wrote to Universities UK, the umbrella organisation for the higher education sector, demanding a crackdown on antisemitism, mentioning Israel Apartheid Week as a cause for concern.

The signatories also express concern about the governments adoption and dissemination of the International Holocaust Remembrance Alliance definition of antisemitism, which it says seeks to conflate criticism of Israel with antisemitism.

These are outrageous interferences with free expression, and are direct attacks on academic freedom, the letter states. As academics with positions at UK universities, we wish to express our dismay at this attempt to silence campus discussion about Israel, including its violation of the rights of Palestinians for over 50 years.

It is with disbelief that we witness explicit political interference in university affairs in the interests of Israel under the thin disguise of concern about antisemitism.

A spokesperson for Exeters Friends of Palestine Society accused the university of censoring students. They are not allowing freedom of speech by cancelling an event that was in support of Palestinian activism and for Palestinian rights, they are directly censoring us.

A university spokesman said: The University of Exeter is committed to free speech within the law and to allowing legitimate protest to take place on campus.

In keeping with guidance from Universities UK, the representative organisation of UK universities, we believe that if protests take place on campus, consideration must be given to the location and prominence of planned events and their impact on the staff and student body, as well as the need to ensure that they do not restrict the ability of the campus community to move freely.

The proposed mock Israeli checkpoint street theatre event was planned for a very busy part of campus where students and staff not only congregate but use as a thoroughfare to lectures. There are other events being hosted by the Friends of Palestine this week where there will be an opportunity for views to be expressed and debated in a safe and inclusive environment.

Exeter was recently the subject of media reports about antisemitism on campuses after a swastika and a Rights for Whites notice were found in halls of residence earlier this month. Last term, students were pictured wearing T-shirts with handwritten antisemitic and racist slogans at a sports club social event.

An investigation was launched into the swastika and Rights for Whites notice at Exeter. A university spokesman said: The investigation has concluded and disciplinary action has been taken in line with the universitys regulations.

Organisers of the Israel Apartheid Week at Exeter claim the university is conflating antisemitism with Palestinian activism. It doesnt have anything to do with antisemitism, said the spokesperson for Exeters Friends of Palestine Society. We feel they were indirectly accusing us of antisemitism and discrimination and harassment through this event.

On Monday, it also emerged that an investigation had been launched after a newly elected students representative at Exeter was accused of publishing antisemitic tweets. Malaka Shwaikh, who is Palestinian, has been elected a vice-president of the students guild at Exeter after promising to improve conditions and opportunities for postgraduate researchers.

She is already a trustee of the guild which launched an investigation after tweets attributed to her by the Campaign Against Antisemitism (CAA) were revealed. Shwaikh has been contacted for comment by the Guardian.

According to the CAA, the day before Holocaust Memorial Day in January she tweeted: The shadow of the Holocaust continues to fall over us from the continuous Israeli occupation of Palestine to the election of Trump.

It also published a tweet from 2015 in which Shwaikh apparently said: If terrorism means protecting and defending my land, I am so proud to be called terrorist. What an honour for the Palestinians!

The CAA raised concerns about material in tweets attributed to Shwaikh from February 2013 when she was drawing attention to the plight of Samer Issawi, a Palestinian prisoner on hunger strike in an Israeli jail. All of the tweets cited by the CAA have been deleted.

Gideon Falter, the CAA chairman, said: So many mechanisms designed to protect students from racist hatred and extremism have clearly failed here, and what is disturbing is that they have broken down in broad daylight and very prominently indeed. Malaka Shwaikh has been very active in promoting her views, yet she has managed to become one of the most prominent figures at the University of Exeter.

In a statement to the Guardian, Shwaikh, 26, said she had been subjected to bullying, harassment, threats and serious defamation of character. She said: I do not need to explain how serious this in in the current global atmosphere of Islamophobia. I should also point out that all of this will no doubt have an effect on my freedom of movement.

Countries do not need much of an excuse to refuse visas to Muslims and a simple Google search of me reveals many of these inflammatory and abusive articles calling me an antisemite and a terrorist.

It will also have serious implications when I return to Gaza. Threats have already been sent to my family back home. A few days ago, someone implied to my dad: Malaka will have to pay the price once she gets back to Gaza.

She said the tweet concerning the shadow of the Holocaust was a follow-up to one in which she said the Holocaust was one of the bleakest chapters in the history of the 20th century. She added: I have never denied the horrific crime of the Holocaust that was inflicted upon the Jewish people, neither have I ever made light of it.

Shwaikh said she understood that the terrorist tweet might seem an extremist statement that would rightly raise concerns. But she said: These kind of statements by Palestinians are most commonly in response to efforts by Israel advocacy groups and the Israeli government to demonise and dehumanise Palestinians ... It is absolutely vital to understand the wider issues before making a judgement on that particular tweet.

She said the February 2013 tweets were not her words but the result of a hack and she removed the messages as soon as she saw them.

Shwaikh added: These attacks against me have been an attempt to defame my character, particularly as a Palestine activist and as a Muslim woman ... I would like to reiterate that I will fight against all forms of racism, including antisemitism.

A spokesperson for the students guild said it was committed to exploring the allegations of antisemitism with a thorough investigation. Toby Gladwin, the guild president, said: The students guild are passionate opponents of antisemitism in all forms; overt or subtle.

The university spokesman added: Our staff and students work tirelessly to ensure everyone feels welcomed, encouraged, supported and embraced, no matter their background, religion or nationality. Antisemitism is not tolerated. Even one incident of discrimination, racism, or harassment is one too many. The students guild, Exeter Universitys student representative body, is responsible for the election of student representatives. It has launched a thorough investigation.

Meanwhile, UCLan cancelled an event called Debunking Misconceptions on Palestine and the Importance of Boycott Divestment and Sanctions, organised by the universitys Friends of Palestine Society.

An initial statement from the university said the event would contravene the International Holocaust Remembrance Alliances new definition of what constitutes antisemitism and would therefore be unlawful.

A later statement to the Guardian said the event had not been referred to the authorities in a timely way and therefore could not go ahead. The content of the event has now been thoroughly reviewed and we are now working with the student society to enable such events to take place, following due process and providing that they are properly managed so that no one in our university community is made to feel unsafe.

The universitys student union president, Sana Iqbal, said: The union supports free speech within the law and hopes that an event that deals with the issues about which this group of students cares very deeply will be able to go ahead in the future. Free speech on campus is an important principle we will stand up for.

Ben Jamal, the director of the Palestine Solidarity Campaign, said there had been coordinated attempts by pro-Israel lobby groups to pressurise universities into cancelling events as part of efforts to suppress activism for Palestinian human rights.

He said: It is important that universities withstand this pressure and uphold both their legal and moral duties to uphold freedom of expression. Discussion of human rights abuses should never be closed down.

This article was amended on 28 February 2017. An early version said UCL cancelled an event called Debunking Misconceptions on Palestine. This should have said UCLan. We also said Jo Johnson recently wrote to UK Universities. This should have said Universities UK. These errors have been corrected.

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Universities spark free speech row after halting pro-Palestinian events - The Guardian