An Irish Muslim teenager has been kept in prison without charge for nearly a year in Cairo because “he is not Irish-looking enough” for the world to take notice, according to his family in Dublin.

Ibrahim Halawa, the 18-year-old son of Ireland’s most senior, Egyptian-born Muslim cleric imam Sheikh Hussein Halawa, was arrested last August along with three older sisters when they caught up in a riot while visiting relatives in Cairo.

The sisters were released in November but Dublin-born Ibrahim has remained in jail where his family say he has been bullied by jailers and taunted that he will be put to death.

The 28-year old sister, Somaia, told the Irish Sunday Independent that her brother “is Irish, he was born here, but he does not look Irish, he does not look like he is from the EU and I think this is why it’s been so slow.”

“It should not matter if our parents are not from Ireland. Ireland has a responsibility towards him. I love and respect this country, but they have never asked me whether I am originally Irish when I am giving them my taxes.”

In November, the then-foreign minister Eamon Gilmore spoke to the Egyptian foreign minister and said he had “expressed the Government’s hope and expectation that the situation would be brought to a satisfactory conclusion in the near future.”

Diplomats from the Irish embassy in Cairo have been visiting Ibrahim and offering consular assistance.

However Somaia said: “We appreciate the help we have got from the Irish Government, but it’s time for action. They have been raising the case long enough and nothing has happened, the fear is killing us.”

On June 21 a court in Minya, Egypt handed down the largest mass death sentence of recent years when Muslim Brotherhood’s spiritual leader and over 180 others were sentenced in connection with an attack on a police station which killed one officer and one civilian.

Last week a Cairo court sentenced three Al Jazeera journalists to seven years in prison on charges related to terrorism.

In a letter to the Irish Times earlier this month, Father Seamus Fleming, a priest of the missionary order the Holy Ghost Fathers and a friend of the Halawa family, pleaded with the prison authorities in Cairo that they “allow a young man who was probably misguided to join his family in Ireland.”

Fr Fleming called Ibrahim “a forgotten Irish teenager.”