Tony Blair today said he wanted to devote the rest of his life to promoting understanding between the world's religions.

The former prime minister recalled how his Christian faith gave him the strength to take tough decisions during his spell in Downing Street.

In his most detailed description of the central role of faith during his decade as prime minister, Blair said religion inspired him even when he thought he had little political support.

His remarks appeared in an interview with Time magazine on the eve of tomorrow's launch of his new Faith Foundation, which aims to increase dialogue and practical work between the world's religions, in New York.

Blair, who travels the world as Middle East peace envoy, as a £500,000 a year adviser to the investment bank JP Morgan and as one of the highest paid speakers on the global lecture circuit, said fostering interfaith dialogue was now his most important work.

"This is how I want to spend the rest of my life," he said.

Blair was wary of talking about religion during his time in Downing Street for fear of being seen "as a nutter", he told a BBC documentary last year.

Alastair Campbell, his former communications director, famously told an interviewer from Vanity Fair: "We don't do God."

The former prime minister, a committed Anglican since his days as a student at Oxford in the 1970s, converted to Catholicism after his departure from No 10 last year.

He told how religion helped him during difficult periods as prime minister, saying: "The worst thing in politics is when you're so scared of losing support that you don't do what you think is the right thing.

"What faith can do is not tell you what is right but give you the strength to do it."

In his Time interview, the former prime minister did not mention his most difficult period in office, the buildup to the Iraq war in March 2003 when he told aides that he would resign if he lost a commons vote authorising military action.

But he made the central importance of his faith clear when he said: "I think faith gives you a certain strength and gives you a support in doing a job as difficult as leading a country and gives you that strength and support."

In a rare comment about his faith during his time in Downing Street, Blair said in 2006 that he accepted that he would be judged by God.

"If you believe in God, [judgment] is made by God as well," he said. This was wrongly interpreted to mean he had sought divine approval for the Iraq war.

Blair will announce tomorrow that that his Faith Foundation, to be run by his former No 10 aide Ruth Turner, will bring together six faiths - Christianity, Judaism, Islam, Buddhism, Hinduism and Sikhism.

He said the foundation would encourage practical work by religious groups to help tackle poverty and disease, and singled out the UN's millennium development goals as an important area.

His first target will be malaria, which kills around 850,000 children a year.

"If you got churches and mosques and those of the Jewish faith working together to provide the bed nets that are necessary to eliminate malaria, what a fantastic thing that would be," he said.

"That would show faith in action, it would show the importance of cooperation between faiths, and it would show what faith can do for progress."