Football's Premier League and top British firms have called on David Cameron to keep his commitment to devote 0.7% of national income on international aid.
The prime minister is under pressure to row back from the spending pledge as government departmental budgets face fresh cuts but business leaders insisted sticking to the funding target would be a "smart investment" as well as the "right thing to do".
It comes as International Development Secretary Justine Greening prepares to outline plans to boost British business involvement in developing countries.
In a speech tomorrow she is also expected to say the Government will work with developing nations to create stronger tax systems and more investable business environments.
Ahead of this month's budget, FTSE 100 companies like BP and GlaxoSmithKline and retailers, including Morrisons, Dixons and IKEA, joined the Premier League in putting their names to an open letter, expected to be published in the Financial Times, insisting it is in Britain's interest to meet its aid pledge.
It states: "We believe this is not only the right thing to do, but is a smart investment. We believe it is both humanitarian and in the interests of the country for you to do this and the case for continuing, well-targeted aid is beyond doubt.
"Aid has contributed to improving education, health, sanitation and other public services in many of the world's poorest countries. This investment in human capital is a fundamental basis for a functioning economy."
Charity leaders welcomed the support from business leaders. Justin Forsyth, Save the Children's chief executive, said: "We are delighted that some of Britain's best known companies have recognised the remarkable progress of British aid and what it is helping to achieve for the world's poorest people.
"Giving children the opportunity to live, to learn and to thrive will be of enormous benefit to the UK in the long term. Aid is working and Britain deserves enormous credit for delivering on its promise to the poorest, hungriest, and most vulnerable people in the world."
Max Lawson, spokesman for IF, a coalition of 150 charities running the Enough Food for Everyone campaign, said: "It is brilliant that business is speaking out in favour of life-saving aid. They know that aid can really help kick start economic growth that benefits everyone. Life-saving aid is basically a hugely smart investment by UK PLC."