Almost 70 academics, including renowned US scholar Noam Chomsky, have called for the "immediate reinstatement" of a Nottingham University lecturer.
Dr Rod Thornton claims he was suspended for writing an article criticising the university's treatment of a student arrested by anti-terror police in 2008.
The 67 professors and doctors, from universities around the world, said they were "deeply concerned".
Nottingham University has said Dr Thornton's paper is defamatory.
In May 2008, counter-terrorism officers arrested and questioned pupil Rizwaan Sabir along with Hicham Yezza, who worked as the principal school administrator at the university's School of Modern Languages.
Mr Sabir had downloaded the manual as part of research for a dissertation, and had sought Mr Yezza's help in drafting a PhD proposal because of his position as editor of a political magazine.
Six days later both men were released without charge.
'Tide of Islamophobia'
In a paper prepared for the British International Studies Association (BISA), anti-terror expert Dr Thornton claimed the university later "refused to apologise to the men" and also began to "resort to defensive measures that attempted to discredit their names".
He wrote: "Untruth piled on untruth until a point was reached where the Home Office itself farcically came to advertise the case as a 'major Islamist plot'."
He also said the document in question had been available from Nottingham University's own library.
The university has refused to confirm or deny whether the academic has been suspended.
A spokesman said: "Academic freedom is a cornerstone of this university and is guaranteed in employment terms under the university's statutes.
"That freedom is the freedom to question, to criticise, to put forward unpopular ideas and views - it is not the freedom to defame your co-workers and attempt to destroy their reputations as honest, fair and reasonable individuals."
The university said staff had legitimately alerted police because the manual was discovered on the computer of Mr Yezza - an administrative worker with "no academic reason to possess such a document".
It also said it had acted in an "ethical, transparent and fair manner" throughout.
In a letter published in The Guardian, the group of scholars, including philosopher and cognitive scientist Mr Chomsky - based at the Massachusetts Institute of Technology (MIT) - said the original arrests were "perceived as being indicative of a growing tide of Islamophobia".
They wrote: "The claims he makes are very serious and should be subjected to a full and proper inquiry: they cannot be ignored.
"We call for the immediate reinstatement of Dr Rod Thornton and call on the University of Nottingham to openly and thoroughly examine the claims made in his research. We also request that an independent inquiry be conducted into the university's actions on this matter."