The trial of Ibrahim Halawa, the Dublin student imprisoned in Egypt, has been adjourned for a 15th time.

The Irishman was arrested in a Cairo mosque in August 2013 during demonstrations protesting the ousting of former Egyptian president Mohamed Morsi.

He and 493 other accused are now not due back in court until November 12th.

Mr Halawa, who is recognised as a prisoner of conscience by Amnesty International, has been held in prison for 1,142 days to date.

A statement issued by the solicitor representing his family said it had long been feared that the trial would not proceed due to its falling on an Egyptian holiday.

"Today has cemented the belief that a trial is now unlikely any time soon," Darragh Mackin of KRW Law said.

"This fact is wholly and entirely unacceptable bearing in mind Ibrahim has now been detained for three years and one month already, since he was a child aged 17, and with no sign of an imminent conclusion."

Mr Mackin said he understood that KRW Law's application for its client's release, lodged on August 18th, was being "actively" considered.

"It is with this in mind that the maximum pressure must now be brought to bear, to ensure that it is met with the appropriate response," he said.

"Today’s development unequivocally strengthens the requirement for the Egyptian president to now directly intervene and ensure he is returned back to Ireland."

'No credible evidence'

Colm O'Gorman of Amnesty International Ireland said the organisation remained "gravely concerned" for Mr Halawa's physical and mental wellbeing.

The 20-year-old's mental health is thought to have severely deteriorated in recent months.

"Ibrahim’s only 'crime' was attending a peaceful protest and his continuing detention represents an inexcusable violation of both international and Egyptian law," Mr O’Gorman said.

"There is no credible evidence against Ibrahim, who faces and a mass trial alongside 493 other defendants.

"A mass trial simply cannot meet the standards required for a fair trial as defined under international human rights law."

The trial process had been expected to conclude in June until a new panel was charged with reviewing video evidence, which essentially restarted the trial, KRW Law has said.

Amnesty International Ireland today reiterated its call for Mr Halawa's immediate and unconditional release, and urged the Irish government to continue its work on his behalf.

The NGO is holding protest against his imprisonment from 5:30pm tomorrow, at the Egyptian embassy in Ballsbridge, Dublin 4.