UNITED NATIONS - At least $1 trillion is needed to help developing countries get through the global financial crisis, UN Secretary-General Ban Ki-moon told the leaders of the world's richest nations ahead of their meeting in London on April 2. "Unless urgent and decisive action is taken to buffer the blows of the global downturn on the most vulnerable, the economic crisis may soon be compounded by an equally severe crisis of global instability," he wrote in a letter released on Thursday to the members of the so-called Group of 20 (G-20). "A prolonged and severe recession, if not addressed boldly with urgent attention given to the needs of the vulnerable, could likewise affect countries and regions with profound consequences for the security and stability of us all." On Wednesday, British Prime Minister Gordon Brown, the host of G20 meeting, said the world's poor and vulnerable won't be forgotten when leaders of top 20 industrialized nations meet in April in London. Speaking with the UN chief at Headquarter in New York, Brown said it was "urgent" that the Group of 20 act to help the world's poorest nations survive the global financial crisis. Because the world economy is interdependent, Brown said the only solution to the current crisis is global. "I think we are recognising that the Washington consensus on economic policy is over - that the old world has gone, that we have got to build a new consensus on economic development for the future," Brown said. "And the message to every country, I think, is that doing nothing is no longer an option." In his letter, Ban called for a four-pronged strategy to prevent the onset of new catastrophes, beginning with "a truly global stimulus package" that meets the needs of developing countries. The UN estimates that the total financing needed to support developing countries through the crisis is at least $1 trillion for 2009 and 2010, he noted, adding that a quarter of the resources urgently needed would be for the protection of the most vulnerable people and countries. "In providing this support you will bolster the global economy, help to underpin your own growth, and secure global stability," he stated. The Secretary-General urged the G-20 leaders to meet the funding needs of the programmes of the UN and the World Bank to enable them to respond effectively to the crisis - including through the proposed Vulnerability Fund - as well as the funding needs of established vehicles such as the Global Fund to fight AIDS, TB and Malaria. He also stressed the need to firmly reject protectionism and revive the Doha round of trade liberalization negotiations to allow real benefits to reach developing nations. "We must avoid erecting new barriers that could slow economic recovery, and trigger grave social consequences." Thirdly, he called for the 'greening' of the global economy, including in poorer countries, with G-20 leaders committing to conclude negotiations and reach agreement on an ambitious successor pact to the Kyoto Protocol, whose first commitment period ends in 2012, in Copenhagen this December. Lastly, he highlighted that "a genuine solution of the crisis requires a new international financial and economic architecture that reflects the changing realities in the world and gives greater voice to emerging and developing economies."