Gordon Brown is to become the United Nations' special envoy for education, furthering his long-standing aim to ensure that all the world's children get the chance to go to school.
The former Prime Minister, who will remain a Labour MP while taking on the unpaid post, will launch a fund aimed at financing schools and training two million teachers.
The move reflects growing fears that the world will miss the millennium development goal that by 2015 all children should be able to attend primary school. Improving education in the poorest nations has attracted less support from rich countries than health and 70 million children are missing out on schooling.
Since losing the 2010 election, the former Labour leader has met world leaders to urge them to ensure the economic slump does not mean their governments renege on their overseas aid pledges.
Mr Brown said it was a "great privilege" to be appointed to his new role, adding: "Ensuring that every child in the world has the opportunity to go to school and to learn is a long-standing passion of mine."