Taoiseach Enda Kenny is being accused of failing in his duties towards Irish citizen Ibrahim Halawa, by not intervening on his behalf.
The Dublin-born teenager, who has been in prison in Egypt since his arrest two years ago, was told yesterday that his trial had been adjourned until October.
He has now spent 716 days behind bars, and the human rights organisation 'Reprieve' claims he has been tortured while in jail.
Today the Minister for Foreign Affairs Charlie Flanagan released a statement saying he is "disappointed" the trial was postponed for the 10th time.
Fianna Fáil TD Mark Daly said it is "disgraceful" that the Taoiseach has not yet called the Egyptian president to demand Ibrahim's release.
"It's unbelievable that the Irish Government aren't using every tool in the diplomatic bag," he said.
"The most important and powerful tool has worked for the Australian citizens, has worked for Canadian citizens … what will work in this case is if the Taoiseach gets on the phone and asks for a presidential decree to see Ibrahim released and returned to his family."
Ibrahim is also supported by Amnesty International, who have previously said it is unlikely he will receive a fair trial.
Lawyers for Ibrahim are warning he could receive the death penalty if he is not released.