David Cameron has described a murderous Islamic State (IS) video featuring a masked extremist and a young boy with British accents as "desperate stuff" from a group that is "losing territory" and "increasingly losing anybody's sympathy".
The Prime Minister said "Britain will not be cowed" by the terror group, which has released footage online appearing to show the brutal killing of five men accused of spying for the UK.
A jihadi is seen waving a gun as he directly mocks Mr Cameron and the RAF bombing campaign against IS in Iraq and Syria.
On a visit to east London, Mr Cameron said: "It's desperate stuff from an organisation that really does do the most utterly despicable and ghastly acts and people can see that again today.
"But this is an organisation that's losing territory, it's losing ground, it's, I think, increasingly losing anybody's sympathy, and this again shows what an appalling organisation we're up against.
"They hate us not for what we do but for what we are - the fact that we are a successful, tolerant, democratic, multi-faith, multi-ethnic nation.
"They hate that and that's why they want to take us on and that's why they do what they do.
"But I know that Britain will never be cowed by this sort of terrorism. Our values are so much stronger than theirs.
"It may take a very long time but they will be defeated."