Ibrahim Halawa has said he has never been a member of the Muslim Brotherhood and does not support their ideology.
Speaking on the Late Late Show, he said he had no interest in politics when he travelled to Eygpt four years ago as a 17-year-old.
He said he had intended going on a holiday to Ibiza with friends that summer but instead went with his sisters to visit extended family in Eygpt.
While there, they took part in protests against the ousting of then president Mohammed Morsi.
Mr Halawa said two friends he met there were shot and killed and he felt he had to do something and became politically active.
He said: "I was going back to a concert [in Ireland] and my friends were going to their graves.....I had to give my opinion on that".
Shortly before they were due to return home to Ireland Mr Halawa and his three sisters were caught up in a siege at a mosque in Cairo in August 2013.
They were arrested and imprisoned.
The Halawa sisters were freed within three months but Ibrahim spent four years in prison during a mass trial.
Tonight Ibrahim Halawa described his time behind bars.
He spent the first four days "in a cell with 170 people that would literally take 30 people", adding "We didn't get proper food".
He said inmates took it in turns to rest on the floor.
Mr Halawa also described being beaten in prison, on one occassion in front of his mother when he lost consciousness and woke up in hospital.
He said while he was imprisoned with members of the Muslim Brotherhood he does not support their ideology.
He said "I would differ with them a lot on so many points.".
He said the rally he attended was not a brotherhood rally but had members of human rights organisations and christians.
Mr Halawa said he will never ever return to Eygpt again and plans to campaign for people falsely imprisoned abroad.
