In this budget George Osborne will propose to cut the tax relief on debt interest, a loophole exploited by multinational corporations to spirit untaxed profits out of the countries in which they operate and into a constellation of tax havens. When rich countries start sounding the alarm on corporate tax avoidance, you know the situation must be bad.

But while rich nations like the UK lose between 0.5% and 3% of revenue to tax avoidance, developing countries are hit considerably harder, losing 6-13%, up to 26 times more. The IMF calculates that every year around $200bn of untaxed income is taken out of poor countries by the international corporations operating on their territory. That is around 50% more than the total amount they receive in aid from rich counties.

It would appear that the notion of poor nations’ “aid dependence” stems from corporations’ tax independence. The Royal Society of Medicine Journal estimates that without the flow of untaxed money leaving the continent, Africa would on average be on course to hit the fourth Millennium Development Goal this year of reducing by two-thirds the under-five mortality rate. Now it will have to wait until 2029.

Christian Aid estimated in 2008 that 1,000 children were dying each day across the developing world from such losses, which are made possible by the financial secrecy offered by tax havens. Britain facilitates this corruption and the related losses for the world’s public finances – including its own – by heading the world’s biggest network of tax havens, which allows the super-rich to anonymously obscure trillions of untaxed and often illegal wealth. We have the world’s most restrictive tax treaties with developing countries, often imposed decades ago, which allow UK companies to renege on their fair share of tax.

On a recent trip to Ghana, I met the African Tax Justice Network, who told me that the abuse of corporate tax incentives cost the economy $2.27bn annually. Labour’s shadow chancellor, John McDonnell, has for many years been agitating against international tax avoidance and has called for a systemic reordering of the global tax system to stop companies from shifting untaxed profits into tax havens. And while I welcome George Osborne’s newfound evangelism on the issue, he is not going anywhere near far enough.

The chancellor originally said that he supported the principle that multinational corporations should make public how much they pay in tax on a country by country basis rather than getting away with their current practice of aggregating their figures to mask their tax dodging. This would mean anyone who wanted to, including the financial press, could see when companies are shifting profits to avoid tax. But days later the Treasury backtracked, dropping this call and instead only supporting the reform process now taking place in the European Commission. The EC, after being lobbied by several multinational corporations, is now of the view that only the tax authorities of the country where the corporation has its HQ – invariably a rich nation – should be made privy to the corporate accounts, not the public. This will mean that developing nations will need to ask rich nations for the information they need to discover if they are being robbed.

As well as honouring his original pledge for country by country reporting – and therefore base erosion and profit shifting (BEPS) – to be made public, the chancellor needs to go much further. Even the strongest BEPS reforms will not solve tax-dodging because it does not solve the deeper problems associated with tax rules and treaties which harm poorer countries.

Britain should require that all of its crown dependencies and overseas territories such as the British Virgin and Cayman Islands attend the anti-corruption summit in May to pressure them to make public the names of the individuals and companies who are hiding untaxed or laundered income on their territories. The government should also launch an investigation into the effects of UK tax treaties on development in poor countries. Ireland and the Netherlands have done this, Britain should do the same.

For too long we have exploited poor countries for our own enrichment. Now we are supporting the exploitation of poor countries for the enrichment of private multinationals. By fixing the global tax system we are also sending a message that Britain supports fair play. We are saying that we support the poor over the rich, the many over the few and public service over private greed.