The year 2005 must be the year of the "new beginning for Africa", Prime Minister Tony Blair has told a Labour rally marking World Poverty Day.
Fair trade is among the parties' calls
It was time Britain and other leading wealthy nations ended the "scandal" of Africa's poverty, he said.
Tory leader Michael Howard said ending world poverty was a "noble" ambition. Charles Kennedy said the poorest nations' debts must be wiped out.
Former US president Bill Clinton gave his support to Labour on the issue.
Joining the Labour rally at London's Old Vic Theatre via a live satellite link from New York, Mr Clinton said those caring about world poverty should back Mr Blair's government.
It was not only "morally right" to tackle poverty and end debt, it would mean the world's wealthiest nations had "more friends" and "fewer terrorists".
"The most generous programme to end global poverty is less expensive than the cheapest war," he said.
International development has taken a low profile in election campaigning, but was pushed up the agenda World Poverty Day, organised by the Make Poverty History campaign.
And each of the three main party's leaders gave speeches to mark a day of campaign events.
Consensus is needed on aid, the Tories argue
Mr Blair said Britain would use its presidency of the G8 leading industrialised nations to make aid for Africa a key priority.
The scandal of Africa wasn't just that thousands of people died needlessly every day, he said.
"The scandal is that they die when, with the right political will and effort, we can prevent their deaths."
Chancellor Gordon Brown also highlighted Labour's push for world agreement on fighting HIV, TB and malaria, and for the cancellation of the world's poorest countries' debt.
Paying tribute to those that had driven the Make Poverty History campaign, Mr Brown said "an end to unpayable debts, the relief of global poverty and a need for the programme of trade justice" was the only way forward.
"It is wrong that the burden of debts of the past should prevent the poorest people of the world from building for the future."
The richest people in the richest countries had a great obligation to the poorest, he said.
He added that for the first time the government had set a timetable for raising overseas development aid to the UN's target of 0.7% of national
income by 2013.
He also called for support for a £4bn plan for a new International Finance Facility which could save five million lives through immunisation schemes.
Mr Howard also backed the Make Poverty History campaign, in his speech at the Tabernacle Christian centre in north Kensington, London.
He stressed fairer trade would enable less developed states to sustain themselves.
But he also called for good governance and the elimination of corruption to ensure that aid reached the poorest people within the poorest nations.
Arguing that trade was the key to enabling poorer communities to achieve sustainability, he said: "I believe that free trade needs to be fairer, and fair trade needs to be freer."
There was an unprecedented level of consensus on the issue with all the main parties agreeing that debts should be cancelled, he said.
But Mr Blair claimed that under 18 years of a Conservative government aid to the world's poorest halved.
Mr Kennedy pledged "unqualified" Lib Dem support for the campaign and argued the world's conscience should be stirred by poverty as it was by wars and natural disasters.
It was in the country's national interest to end world poverty because security and prosperity were so closely interrelated, he said during a speech to party activists in Barnes, south-west London.
"Britain is a wealthy country, a prosperous country. It is the duty of countries such as ours, with the means to help, to take action to make poverty history," he said.
"For too long, Britain has been slow to match our international responsibilities with action and resources."
He accused the government of a "poverty of ambition" in aiding the world's poor and said his party would ensure Britain met the target of putting aside 0.7% of GDP for development assistance by 2011.