Hawzah News Agency - Dr Umar Al Qadri was speaking following reports from Syria that an Irish passport holder has been captured by Kurdish-led forces fighting so-called Islam state.
The man who is in his mid-40s is originally from Belarus was known to gardaí as an ISIS sympathiser before he left Ireland with his wife and family in 2013 to fight in Syria.
He came to Ireland in 2000 and lived and worked in south Dublin for a number of years.
Gardaí said he was not known to them when he was granted citizenship but was subsequently radicalised by an individual whom they say also radicalised a number of other people here.
Dr Qadri said today that naturalised Irish citizens who leave to fight abroad should be not be accepted back in Ireland but deported to their countries of origin.
He described them as dangerous people who remain so even in jail because they may radicalise others.
He also criticised Taoiseach Leo Varadkar's comment that consular assistance would be available to any such person abroad.
Dr Qadri insisted that Ireland needs to send out a strong message to people who have chosen to leave the state and fight abroad that this country is against extremism.
There is precedence for deporting people who are considered a threat to the State and the courts have upheld the right of the State to do so.
One such person whom gardaí say posed a serious threat to the security of the State and radicalised a number of people while here has already been deported and a second case is being challenged and is currently before the Supreme Court.