Most of the 670 Anglican bishops attending the Lambeth Conference, led by the Archbishop of Canterbury, Dr Rowan Williams, moved slowly and silently behind a banner telling governments to Keep the Promise Halve Poverty by 2015, past Downing Street and the Houses of Parliament to Lambeth Palace.

The Prime Minister told the bishops, who had been joined by up to 1,500 faith leaders, diplomats, politicians and heads of charity, on the march, that "100 years is too long to wait for justice and that is why we must act now".

Mr Brown joined Dr Williams in warning that time was running out if the Millennium Development Goals (MBGs), set in 2000 to halve poverty by 2015, were to be achieved.

Mr Brown told the bishops at a rally in the courtyard of Lambeth Palace: "This is one of the greatest public demonstrations of faith that this country has ever seen.

"You have sent a symbol, a very clear message with rising force that poverty can be eradicated, poverty must be eradicated and if we all work together for change poverty will be eradicated."

The aim of the march, despite potential splits in the community over gay or women priests, was to unite in what was dubbed as a "walk of witness and solidarity" as a powerful voice against poverty.

Dr Williams handed over a letter to the Prime Minister on behalf of the Anglican community, stressing the urgency of action.

In the letter Dr Williams echoed Mr Brown's belief that the goals would not be met.

The march was an attempt to ratchet up the pressure on world leaders ahead of talks at the United Nations on the fulfilment of the Millennium Development Goals.