Microsoft founder and philanthropist Bill Gates joined leading Anglican and Roman Catholic  clerics at the weekend in London to call for mass action against hunger, saying there is no excuse for it in the 21^st century.

They were speaking ahead of the upcoming summit of nations from the powerful G8 (Group of Eight) countries that will take place in Northern Ireland on June 17 and 18.

The Archbishop of Canterbury Justin Welby, representing the Church of England and the Anglican Communion, and the Catholic Archbishop of Westminster Vincent Nichols first spoke at an ecumenical service Saturday urging action at the G8 summit to tackle the root causes of global hunger.

In his message to the ecumenical service in Methodist Central Hall in Westminster,  Welby said: "In many parts of the world, the churches are the most effective networks, through which generosity from other people can be used most effectively."

He said churches can be used, "without actually displacing or diminishing the work of the people on the ground locally - local people developing their own countries."

He noted, "My prayer would be that in this country and across the world, that we are deeply committed to enabling people to be self-sustaining, so that global hunger can be ended in our lifetimes."

Christian agencies and groups from around Britain were prominent among around 45,000 people at Hyde Park for the rally organised by Enough Food for Everyone IF.

Behind it were church-backed agencies such as CAFOD, Christian Aid, Tearfund, Progressio and a coalition of more than 200 development agencies and religious groups.

Archbishop Nichols, the Catholic leader in England and Wales said, "That millions go hungry every day is a responsibility we all must share. These are our brothers and sisters and their suffering is also ours.

"There can be no excuse that in a world of plenty, so many go without. We have gathered today to show our solidarity with those millions who are made to have less because the food system is skewed in favor of those with both financial and political power."

He said there could be little justice when a tiny minority can "hoard spoils" earned by the many.

"And a world where human flourishing, the opportunity to reach our full potential, is the preserve of some and not others is a place that has failed to put people at the heart of politics and business."

The G8 consists of Britain, Canada, France, Germany, Italy, Japan, Russia and the United States. At their annual Summit they join other leading nations in discussing pressing world issues.

"The G8 leaders' meeting in the coming days must tackle the issues at the heart of this unfairness – from tax, to transparency, to resource grabs, to aid that must be carefully and specifically targeted so small farmers can benefit," said Nichols.

In a video address later to a rally in London's Hyde Park organized by the IF campaign, Archbishop Welby said there was an opportunity to "end hunger in our lifetimes."

While he praised the UK Government for spending 0.7 percent of the country's GDP on international aid, he urged activists to "keep the pressure on," noting, "We can change the world in our own lives".

Microsoft founder Bill Gates spoke at the rally saying , "Thank you for coming down here today and asking your government and world leaders to pripaio ritize issues that affect the world's poorest."

"Using your voice to show the world you care makes a real difference."

Gates added: "The UK is keeping its promise to the world's poor, largely because all of you remind your leaders regularly, and loudly, that this stuff matters. Now is our chance to make a significant difference."