Former prime minister Tony Blair has defended religion, warning that a world without faith would be one on a path to "tragedy and disaster".

The ex-PM, who converted to Catholicism after he left office in 2007, said he believed that the sense of something "bigger and more important" than you was "deeply important" for the health of society.

"For a long period of time, what people thought was that as society became more developed and as we became more prosperous, that faith would be relegated, that it would become a kind of relic of the past - what kind of ignorant people do but not what civilised, educated people do," he said.

"I think a world without faith would be a world on the path to tragedy and disaster, I really believe that."

He added: "What is the essence of our faith besides all the things we believe, certainly as Christians, about Jesus Christ and his place in our lives?

"It is also fundamentally a belief that there is something bigger and more important than you, that you are not the only thing that matters, that there is something that is greater and transcendent.

"I think that essential obligation of humility for humanity is deeply important.

"It is what allows us to make progress, it is what keeps us from ideology or thought processes that then treat human beings as if they were secondary to some political purpose."

Blair was speaking to around 4,000 people at the Royal Albert Hall in London at a conference on leadership organised by the Holy Trinity Brompton Church.