Boris Johnson says boy in Isis video is victim of child abuse and calls for him to be brought home

The London Mayor says UK has 'duty of care' towards the boy, who has been identified by his grandfather

The small child with a British accent points to spots he would like prisoners to be executed

Boris Johnson says Britain has a “duty of care” for the young child featured in Isis’s new execution video, and said his treatment by the militant group amounted to “child abuse”.

The London Mayor said the child, who has been identified by his grandfather as the son of British Muslim convert Grace Dare, should be taken away from his mother and returned to the UK.

Isa Dare was taken to Syria when his mother travelled to join extremists in the Middle East in 2012. He appears at the very end of an 11-minute film released on Sunday, pointing into the distance and saying “we will kill the kuffar [non-believers] over there”.

Mr Johnson told LBC radio: “It's heart-breaking what's happening to that kid. He can't possibly know or understand what he's saying or what he is being made to say. This is child abuse, there is no question at all.

He went on: “This child is a victim of child abuse and he is, as I understand it, a British national. I think we have a duty of care.

Like Siddhartha Dhar, the lead suspect in the hunt for the masked man seen speaking in the video, Ms Dent was raised and educated in London.

Mr Dhar converted from Hinduism to Islam and became a key member of the now-proscribed al-Muhajiroun group. He was being investigated on terror charges when he skipped bail in 2014 to join Isis in Syria.

Mr Johnson said he would be speaking with the Metropolitan Police about how Mr Dhar, now going by the name Abu Rumaysah, had been able to leave the UK.

“I'm raising that with the police,” he said. “I will be discussing that with the police later today. I'll need to understand the circumstances in which that decision [to release him on bail] was taken.”

The Mayor was also asked about why it is that so many British foreign fighters for Isis, including the so-called “Jihadi John” Mohammed Emwazi, appear to come from London.

He said: “It absolutely grieves me and it's because there has been for a long time in our educational culture an idea that it's all relative and everybody's values are the same.

“That isn't good enough for me - I want everybody to feel that they belong to this society, to feel that the values of pluralism and tolerance are absolutely vital.”