Egypt has been accused of telling lies to the Irish Government over the continued detention of student Ibrahim Halawa.

The campaign group Reprieve says the Egyptians area also lying to the United Nations over the continued detention of the Dublin student who was 17 when he was arrested in Cairo in 2013.

He is being tried alongside 493 other people in mass proceedings, which have been repeatedly postponed in the last three years.

Reprieve claimed that Ibrahim is believed to be held in poor prison conditions, and has reported being tortured and threatened with execution throughout his detention.

During visits to him, Irish consular officials have noted “serious marks and bruising” on his body, they said.

In the urgent appeal, sent to the Egyptian government last year, the UN experts had called on Egypt to respond to evidence of Mr Halawa’s mistreatment, and to reply to concerns about the fairness of his arrest and mass trial.

In a response, revealed by the BBC, the Egyptian authorities said any allegations that Ibrahim's health was suffering were “false”, and claimed that he had “no recent injuries.”

The pressure group alleged that the Egyptian submission contained no reply to the observations of Irish consular officers who witnessed marks of torture on Ibrahim’s body; it also failed to respond to accusations that Ibrahim has been denied access to a lawyer, and threatened with further execution.

The document has emerged after the Egyptian government was recently accused of misleading Irish consular officials on Ibrahim’s case.

Earlier this month, it emerged that Ibrahim had been moved from one prison to another without the knowledge of Irish officials, or the Halawa family.

In a report last year on the death penalty in Egypt, human rights organization Reprieve – which is assisting Ibrahim – found that over 70pc of recent death sentences in Egypt were handed down in relation to political protests.

Harriet McCulloch, deputy director of the death penalty team at Reprieve, said: “The UN and the Irish government should be in no doubt that the Egyptian authorities are telling outright lies about Ibrahim’s case.

“The reality is that he should never have been imprisoned in the first place – he was arrested as a child and did nothing wrong, and yet he has been through torture, hellish prison conditions, and an appalling mass trial that could see him sentenced to death.

“The Egyptian authorities must stop peddling falsehoods about Ibrahim's case, and instead release him without delay.”

Online Editors