There’s a big argument taking place over whether in these straitened times we should be continuing to fund foreign aid programmes. It’s quite right that we have this debate – taxpayers’ money should be spent only if this is achieving good results. My view is clear: aid works.

Take one statistic. Between 2011 and 2015, Britain helped vaccinate 67 million children, saving at least 1.2 million lives from diseases such as pneumonia and diarrhoea. Such financial help doesn’t benefit just the countries that receive that aid: money spent on international development is an investment in our own security. Because if we don’t tackle poverty abroad, the results are visited upon us at home. Mass migration, epidemics such as Ebola, climate change and pollution: none of these things respect national borders.

Here’s another statistic. In 1950 the population of the Middle East and Africa was equivalent to half of the population of Europe. By the end of this century, it will be eight times the size of Europe’s. If we don’t play our part in ensuring that everyone has an education and hope of a decent life, then the waves of migration we have seen in recent years will be nothing, compared with in decades to come.

So my view is that the debate shouldn’t be whether we spend money on aid: it should be how we spend that money. The answer is to shift our focus to address the failure of states to govern effectively, which is increasingly responsible for the suffering we see around the world.

It used to be said that geography is destiny. It’s not. More than climate, culture or history, it is the strength of a country’s political systems that determines whether its people live in poverty. As it has been put before, bad governance is the main reason poor countries are poor. Governance is destiny.

There are so many countries where the governments lack legitimacy or authority, and where corruption, conflict and violence are rife. These governments are frequently unable to provide the most basic services, such as healthcare, education, security or infrastructure. The building blocks of democracy, such as a fair judiciary and the rule of law, are often completely absent. Crucially, there is no prospect of the creation of an effective private sector – and, with it, jobs. These are, in the development lingo, “fragile states”.

I’ve seen the effects at first hand, from Sudan to Afghanistan: gilded presidential palaces next to slums; people seeking justice from extremist organisations because there is no rule of law.

As prime minister, I made sure that half Britain’s aid spending went to the most fragile states. With our presidency of the G8, we put tackling corruption at the top of the international agenda, as well as three of its cures: more transparency, fairer taxes and better trade. Today, state failure is increasing – and nearly half the world’s poor people will soon live in fragile states and regions.

At the same time, there are huge gaps in our understanding of what makes states fragile, and keeps them that way. And much of the work that has been done has yet to be translated into workable policies.

That is why I am chairing the new Commission on State Fragility, Growth and Development, with Oxford University’s Blavatnik School of Government and the London School of Economics.

My co-chairs will be Donald Kaberuka, the special envoy of the African Union Peace Fund and the former president of the African Development Bank, and Adnan Khan, research and policy director of the International Growth Centre. Sir Paul Collier and Tim Besley, two of the world’s finest minds on development and economics, will serve as academic directors.

We will be joined by eight other commissioners from around the world to take evidence from everyone from military commanders in Afghanistan to aid workers in Syria. We want to generate the most cutting-edge recommendations that governments, donors and NGOs can put into practice. This may destroy some long-held shibboleths. It may show that, when it comes to aid, there should be more investment in security. It may show that the building blocks of democracy – critically, the rule of law – are more important than the act of simply holding elections.

One crucial question we hope to answer is how to enable the private sector to play its role. Because it is not just big companies but small and medium enterprises that are the bedrock of successful economies and vibrant societies.

Another is how to help governments create a tax base so they can pay for their own development. With some fragile states raising only 12% of their GDP from tax revenue, there is much to do.

From defeating fascism and communism to spending 0.7% of our national income on aid – the only major economy to do so – Britain has always led the way when it comes to making this a safer, fairer, more prosperous world. Maximising every aspect of our soft power is even more essential in a post-Brexit world. And keeping our promises on aid makes us uniquely well placed to argue for a new approach.

This new commission is determined to play its part.