Academics from across the globe have condemned Murdoch University’s treatment of a whistleblower who spoke out about international student exploitation, saying they are “appalled” at what they see as an “extraordinary” attempt to intimidate him and others into silence.

The university is suing associate professor Gerd Schröder-Turk for criticising its treatment of international students during an episode of the ABC’s Four Corners.

Schröder-Turk alleges the university retaliated against him within days of the program airing, and he is now attempting to engage Western Australia’s whistleblower protections.

But the university has launched a cross-claim in the federal court alleging Schröder-Turk’s comments damaged its revenue and international student enrolments. It is reportedly suing him for millions in damages.

The university’s actions have prompted withering criticism from a group of 23 academics in Australia, Germany, Denmark, Sweden, Canada, Switzerland and the United States.

In a joint statement to the Guardian, the academics said the legal action was clearly designed to keep Schröder-Turk and other whistleblowers silent.

“We are appalled by the continued harassment of Schroeder-Turk,” the group said. “The legal suit against him is designed to intimidate him, and future whistleblowers into silence.

“This is extraordinary behaviour from senior ranks of an institution dedicated to higher learning.”

The academics include three fellows of the Australian Academy of Science, writing in their personal capacity, 10 academics from the Australian National University, four from the University of Copenhagen and others from Sweden’s Lund University, the University of British Columbia, the University of Illinois and the University of Fribourg.

During the ABC program, Schröder-Turk said the university was admitting international students who did not meet its standards for English. He feared the practice was setting the students up to fail, posing a risk to their welfare and jeopardising academic integrity.

The group of academics previously wrote to Murdoch University’s vice-chancellor, Eeva Leinonen, in May, expressing concern about the response to the allegations, particularly suggestions that the Four Corners program had racial overtones.

“We are appalled by your labelling of such criticism as ‘racist’, which deters from the substance of the debate and comes across as a personal attack,” they wrote.

“Schroeder-Turk and his colleagues are trying to protect the international students from exploitation while ensuring the long term reputation of Murdoch University is maintained. We can only conclude that your response is designed to silence concerns for international students’ welfare, as well as those of domestic students and academic staff.”

Their letter received no response.

The group said the non-response showed the vice-chancellor either saw the concerns as an “intrusion on internal business, or a nuisance to be ignored”.

“Either way, she is wrong,” they said. “We consider the attacks on Schroeder-Turk and his colleagues a dangerous precedent. It must be challenged, in order to maintain the ideal of a university as a forum for open debate and fearless exposure of dubious practices within academic institutions in Australia.”

The treatment of Schröder-Turk has also prompted condemnation from the Australian Institute of Physics, of which he is a member.

The institute issued a statement on Tuesday saying it “supported the right of staff and students of academic institutions to respectfully question their organisations”. It said it stood with Schröder-Turk, and urged the university to drop its legal action.

The case has again highlighted the flaws in whistleblower protections. In many jurisdictions, retaliation against whistleblowers such as Schröder-Turk forces them to resort to costly and protracted court action.

The opposing institution often has greater resources to sustain a lengthy court case.

“Western Australia’s Public Interest Disclosure Act is one of many laws across Australia which are still overdue for reform to better address these issues,” Griffith University integrity expert, AJ Brown, said this week.

Murdoch University was approached for comment.