The African Development Bank will launch an initiative to help countries on the continent better prepare for credit ratings, President Sidi Ould Tah said on Thursday.

"What is missed in Africa is the data and the infrastructure...the opacity in some markets creates this notion of high risk, which leads to high cost of borrowing," Tah said at the S&P emerging markets conference in London.

African leaders have long said that funding costs on the continent are unfairly high.

The "big three" ratings agencies say their ratings follow the same formula across the world.

The African Development Bank will soon launch an initiative via the African Legal Support Facility to help countries prepare for ratings through better data and more transparency, Tah said.

Tah said improving credit ratings was a common goal across the continent, with only 3 out of 54 nations currently investment grade.

The African Peer Review Mechanism - an African Union-backed initiative - plans to launch a continent-wide ratings agency this month that also aims to tackle high borrowing costs.

The AfDB is also leading a continent-wide effort to enable more local financing, and Tah said it has met a range of stakeholders including pension funds and banks to identify and address impediments to the development of strong capital markets and domestic resource mobilisation.