Rock star Bob Geldof called on the Group of Eight rich nations on Tuesday to honour their commitment to double aid to Africa by 2010.

The G8 agreed the aid increase at its 2005 summit in Gleneagles, Scotland, but a report last month by the Africa Progress Panel said that under current spending plans the G8 will fall 40 billion dollars (20 billion pounds) short of its target.

"They should be at a 50 percent point in their commitment, but in fact the G8 are only at 14 percent," former Boomtown Rats singer Geldof, who is lobbying the summit on the northern Japanese island of Hokkaido, told the BBC.

"They promised, they wrote out, they signed their names on a political contract between rich and poor and that promise must be kept."

Geldof praised the work Britain, the United States and Germany were doing to live up to their aid commitments to the world's poorest continent, but was less complimentary about Japan.

"Britain leads the pack by a million miles and they've always made the running. Surprisingly the U.S. will get there by 2010 and Germany has come up on the inside track and have joined the good guys.

"The Japanese doubled their aid to Africa four weeks ago, but it's smoke and mirrors. What they did was they took the exact money they needed to double their bilateral aid from their multilateral budget.

"So they have a shortfall in their multilateral budget, but they didn't promise that at Gleneagles. You've got this going on all the time."

Despite those criticisms, Geldof had words or praise for the G8 leaders in the benefits the 100 percent debt cancellation agreed at Gleneagles had brought to Africa.

"There has been great progress - 29m children in school for the first time and 2.4m people with AIDS on retroviral drugs. In 2002 there were only 50,000 on those drugs and they had to pay for it and now it's free."