Obama said that during his presidential campaign in 2008, when social media and technology was gaining traction, he had seen them as a beacon for hope

But he said the same positive forces and tools that could mobilise people around democracy or human rights could also be used by hate groups.

He said they "connected people for good, but also for ill".

"It turns out that the reptilian side of our brain really gets attracted to anger, fear, resentment and the sense that someone is out to get you," he said.

"So a lot of social media and a lot of our information is informed around that."

But the former president, who has already spoken in Belfast and will appear in Manchester on Thursday night, said that a drift towards extremism was "not inevitable".

He added: "After World War Two, at least in the United States and certainly in Europe as well, the federal government said 'we're going to set up some rules because we've seen what propaganda can do in the hands of somebody like Hitler.

"We can see how big lies and misinformation can distort and enrage and incite violence. So we're going to hold these folks responsible'."

"We have not chosen to do that."

Speaking about hope, Obama was asked if he still believed in a Martin Luther King Jr phrase he quoted years ago, about the arm of the moral universe being long, but ultimately bending towards justice.

The former president said that he still stands by the quote and argued that hope is an active "almost theological" choice people must make.

He said: "It is a decision about how do we face and embrace this finite amount of time we have on the planet."

He told the audience he believes it is healthier for people to believe that change is possible.

"I think when we act on that basis, it doesn't always work out, but over time things do get better," he said.

Obama also said there seems to be a cycle in humanity where people forget lessons learned from the past and start to take things for granted.

"We start thinking 'maybe using language in public from our politicians that fosters hatred and scapegoats certain people – immigrants, Jews, or blacks or gays – that's just talk, it's humour'."

He said people forget where that can lead to, with them becoming less tolerant.

Obama told the audience that the world is going to be dealing with "big challenges", but he said he thinks "we can be better" and that making the world better remains worth fighting for.