Talha Asmal, 17, reportedly left Britain recently and then detonated a vehicle fitted with explosives while fighting for Islamic State in Iraq.
His attack on an oil refinery in the city of Baiji left 11 people dead.
Islamic State used social media to indicate the teenager was one of the men involved in the bombing.
It has led to more calls to find ways to identify young British Muslims who could be radicalised.
But Christian and expert in Islamic Affairs, Dr Anthony McRoy, told Premier's News Hour the focus should be on the victims of the attack.
"This young man made a conscious choice," he said, "we've got 11 people who've been killed as a result of this, now that's where our focus should be, on the victims of this incident, not this young man."
The attack means Asmal, from Dewsbury, West Yorkshire, is now Britain's youngest known suicide bomber.
In a statement his family said he was a "loving, kind, caring and affable teenager" who never "harboured any ill will against anybody nor did he ever exhibit any violent, extreme or radical views of any kind".
But Dr McRoy told the News Hour the family would not have known what was going on: "We've got to step back from what the family are feeling, the family are obviously grieved, they're obviously ashamed about this.
"But we need to go to a more objective source to find out what happened here.
"The simple fact is we can say definitely it was his choice to leave the country and go the Islamic State, it was his choice to go and fight for them.
"It was his choice to engage in this attack which brutally murdered 11 people.
"We have to let him take responsibility for his actions."
The Prime Minister's official spokeswoman said David Cameron was "clear that the case is deeply concerning, and that it underlines the need to do all we can to prevent young people being radicalised and, if they are thinking of travelling, to stop them from doing so."