The former Prime Minister will use the speech to announce plans for his new Faith Foundation to organise a global campaign among young people of all religions to improve conditions for the world's poorest.

Mr Blair will highlight the importance of faith as a progressive force in the modern world and the need for people of different religions to work together in the first of a series of lectures by public figures on faith and life in Britain at the mother church of Roman Catholics in England and Wales.

He will say the Tony Blair Faith Foundation - due to be launched later this year - will bring Christians, Muslims, Jews, Hindus, Sikhs and Buddhists together to achieve the UN's Millennium Development Goals.

The eight goals include eradicating extreme poverty and hunger, providing universal primary education and combating HIV and Aids.

Calling on faith groups to do more, he will say: "The Millennium Development Goals are stark in their ambition and necessity.

"We are falling short as a world in meeting them. It would be a great example of faith in action to try to bridge the gap and awaken the world's conscience."

Around 1,600 people who applied for free tickets to hear the former Premier will be present in the Cathedral in central London to hear the address.

The speech comes after Mr Blair stood down as PM in June last year with many observers believing his departure from office was hastened by his decision to commit British troops to Iraq.

His address will be preceded by a silent vigil outside the Cathedral mounted by Pax Christi UK, the Catholic peace activists, followed by a noisy "wall of sound" demonstration by anti-Iraq war demonstrators from the Stop The War Coalition.