Britain and France have both announced they are to join a groundbreaking initiative to expose systematic corruption, mainly in Africa, requiring mining and oil companies to reveal the taxes paid to national governments and the value of the minerals being extracted.

Nearly 40 countries have already signed but the news that France and the UK have joined the initiative represents a breakthrough.

The decision to join the Extractive Industries Transparency Initiative was announced by the French president, François Hollande, and the British prime minister, David Cameron, ahead of a working dinner in Paris.

The UK helped create the EITI in 2002 and has subsequently funded it, but since the UK was not defined as a "resource-rich" country by the International Monetary Fund, the UK did not feel it necessary to join, even after Barack Obama said the US would join in 2011.

Under the initiative, annual reports publish what tax was paid by oil and mineral companies in a country, and the national government publishes what it received. The report is prepared to an international standard overseen by an independent body. The two sums are then reconciled and any gap can be often be attributed to corruption. The move also strengthens the powers of the legislature of countries since they have clearer information on what their executives have received.

The current chair of the EITI is Clare Short, the former international development secretary. In a weekend interview she said: "This is billions and billions and it far outweighs anything that goes across the world in aid. If these monies were properly managed and properly invested and used, hundreds of millions, literally, of people could see a better life. At the moment there's great riches but they're not lifting up the people in poor countries that have become the target of mining and oil investment in this commodity boom in the way that they should."

She said: "You can't force countries, but if a country won't reform and in the worst case that you talk about where you've got a kleptocracy that really is running away with the money, no one can make them change unless they want to.

"But the EITI does leverage change in improvement in some of the countries with really serious problems."

In Washington last week, David Cameron the current chair of the G8 leading economies, called for more openness among energy companies, claiming a veil of secrecy obscures the conduct of the extractive industries.

He announced an urgent review into Britain's failure to join the regime, saying: "We cannot call on other countries to live up to these high standards if we are not prepared to do so ourselves."

The US Securities and Exchange Commission ruled last year that oil and natural gas companies must disclose payments to foreign governments.

At present there are 39 countries involved with the initiative and 23 that are fully compliant.