LONDON (Reuters) - Tony Blair's spokesman once said "We don't do God." He certainly does now.

The former Prime Minister has gone public over his beliefs in a major speech on faith, saying religion had to be rescued from extremism in an era of growing globalisation.

Speaking in Westminster Cathedral on Thursday evening against a noisy backdrop of anti-Iraq war protesters, Blair launched an impassioned defence of religion.

Blair, who converted to Catholicism last year after stepping down as premier, rejected the notion that religion was divisive, irrational and harmful and argued "Faith can transform and humanise the impersonal forces of globalisation."

"For religion to be a positive force for good, it must be rescued not simply from extremism -- faith as a means of exclusion -- but also from irrelevance," he added.