When the G-20 leaders meet in Pittsburgh, recovery and reform of global financial systems will be key agenda. They will discuss new regulatory regimes and cooperation to jumpstart global economic growth, trade and investment.

For half the world's population, however, decisions taken at the G-20 will have little or no effect. This is because more than 2.5 billion people around the world have no access to formal financial services, such as bank accounts, savings accounts, credit, or insurance.

About 95 per cent of these are in developing countries, most on less than $2 a day.

This gap is a significant barrier to economic growth. Expanding financial services to the world's poorest would increase savings and, in turn, provide new funds for investments in agriculture and small and medium enterprises, which is critical in creating jobs.

Some of the smartest policies to expand financial access have come from poor countries, such as mobile phone banking in Kenya and the Philippines, agent banking in Brazil and Peru, and state bank reforms in Indonesia and Thailand. Unfortunately, knowledge of these programmes is yet to be widely shared.

That is beginning to change. This week, leaders from developing countries met in Nairobi to launch the Alliance for Financial Inclusion (AFI), a global network of central banks, finance ministries, development agencies and other policymakers to identify, create and share solutions to bring the world's poorest into the circle.

The first key task will be to bring financial services to 50 million people who earn less than $2 a day -- equivalent to the population of South Africa -- by 2012.

The opportunities created by the rapid expansion of mobile telephony are promising. It is estimated that by 2012, the number of people around the world without a bank account but with a mobile phone will hit 1.7 billion.

In Kenya, a mobile phone money transfer service called M-Pesa launched just over two years ago has attracted more than 7.4 million registered customers by July 2009, or 19 per cent of Kenya's total population of about 39 million, and over 12,000 agents with a transactions value of almost 20 per cent of GDP every month.

Bringing the world's poorest into the financial services sector faces a myriad of challenges. We need to ensure that people are not exploited as happened with pyramid schemes in Kenya. AFI members will explore these challenges as they work to bring banking, savings and insurance to more of the world's poor.

We must help foster the spread of new and innovative ideas and initiatives to deliver these services to the world's poor to take advantage of its opportunities.

Prof Ndung'u is the Governor, Central Bank of Kenya.