Thousands of campaigners including pop star Ronan Keating and actor Pete Postlethwaite are set to march on the Treasury.
They are demanding that the Government cuts funding to the World Bank and the International Monetary Fund (IMF).
The rally will call for both institutions to reform and stop pursuing damaging policies that harm poor people in developing countries.
It has been timed to coincide with two days of World Bank and IMF meetings in Singapore, which start on September 18 and will be attended by the Chancellor, Gordon Brown.
Campaigners hope that the radical call will persuade the organisations to follow Tony Blair's decision, made after the Make Poverty History campaign, to stop the UK forcing poor countries to implement controversial economic policies in return for aid.
Keating, who first shot to fame with Boyzone, said he was backing the campaign because he has seen the "negative" effects of IMF policies with his own eyes.
He said: "I met Ghanaian chicken farmers who are struggling because of pressure from cheap frozen imports from Europe. The government in Ghana, like governments in many developing countries, is not allowed to help its farmers with subsidies or protect its own chicken market with higher tariffs on imports.
"When they did try, the IMF put pressure on the government to back down."
Ibrahim Akalbila, who works for Christian Aid's partner organisation ISODEC, has come to the UK to take part in the rally.
He will meet with International Development Secretary Hilary Benn to tell him how IMF policies are stripping poor Ghanaians of their livelihoods. He said: "Thousands have been laid off. Many businesses have collapsed. People are drowning."
