A British academic being held in solitary confinement in the United Arab Emirates on suspicion of spying is said to be suffering from "significant health issues".
Matthew Hedges, a 31-year-old PhD student at Durham University, was arrested after travelling to Dubai in May to conduct research about the country's foreign policy and security strategy.
He has been held in solitary confinement ever since.
In a joint statement Durham and Exeter universities said they are "deeply concerned" about Mr Hedges's welfare.
The statement said: "Matt is suffering from significant health issues after more than five months in detention.
"His welfare and right to a fair trial are now the overriding concerns of both Durham and Exeter universities."
Both universities called upon the authorities in the UAE and the UK to "treat Matt with proper fairness and to make every effort to return Matt to his wife, Daniela, and his family and friends".
They added that the court has been assured of Mr Hedges’s status as a PhD student "in good standing".
Mr Hedges completed a Masters degree in Middle East Studies at Exeter, and began working on his PhD at Durham in 2013.
The universities said: "Matt’s thesis is nearing completion and was carried out in full accordance with Durham University’s research and ethics procedures.
"His academic colleagues speak highly of his work, noting both his diligence and level of scholarship, as well as his undoubted passion and care for the Arab Gulf and its people."