Bob Geldof refuses to back down, insisting that Prime Minister Paul Martin should be ashamed of his government's refusal to increase the level of Canadian aid to Africa.

In an interview Wednesday morning, Geldof said Martin has an obligation to make good on a promise made by then-prime minister Lester B. Pearson 35 years ago -- to allocate 0.7 per cent of the country's GDP to aid.

"Canada's signed up to this," Geldof told CTV's Canada AM. "At what point will a sovereign state -- through its government -- live up to its promise?"

The powerful, he added in a terse rebuke, cannot break a promise made to the weak.

"The honour of a country is signed off when you sign those documents."

Geldof, who is behind the upcoming Live 8 series of concerts intended to focus world attention on poverty, says Canada would do well to join the five European G-7 countries that recently agreed to double their foreign aid by 2015.

Doing so would underscore the conspicuous lack of support from Japan and the U.S., Geldof said.

Noting Canada's status as the only G-7 nation with a budgetary surplus, he believes the opportunity should be obvious. "Don't you think you could take a leadership role on this?"

On Tuesday, the day that details of the Live 8 Canada concert were announced, Geldof told Martin he shouldn't bother going to the G-8 summit in Scotland unless he arrives with a promise to increase contributions.

At the urging of NDP leader Jack Layton, the prime minister responded to the comments in the House of Commons daily question period.

Martin said he supports the 0.7 per cent goal, but also said it's just as important for governments to say how they'll achieve the goal.

"I believe in the 0.7 and I would very much like to see Canada get there by the year 2015. But I'm not going to make a commitment that I'm not sure the government will be able to keep.

"Too often commitments are made on the grounds of photo ops and I will not do that."

Geldof is the just the latest pop culture icon to berate Martin for his government's policy on aid to Africa.

In April, U2 frontman Bono told a crowd at a Vancouver concert that he was disappointed the prime minister hadn't delivered on a pledge to reach the 0.7 per cent level by 2015.

Ottawa has pledged to boost its international aid budget by eight per cent each year, with the goal of someday reaching the 0.7 per cent level.