Bono said he was disappointed Martin had not kept an earlier promise to boost Canada's foreign aid to a level equivalent to 0.7 percent of gross domestic product.
"I'm bewildered really. I'm disappointed. I've not given up hope. I really can't believe that Paul Martin would want to hold up history, or indeed would hold up history," Bono told CBC radio in an interview broadcast Saturday.
Bono, a tireless campaigner on behalf of the poor in Africa and other regions, also read out the number of Martin's office and urged Canadians to flood his office with telephone calls.
"We were looking for Canada to lead rather than be a laggard ... what's upsetting about this is it feels like business as usual," added the star.
Bono's annoyance contrasts sharply with his November 2003 address to a conference of the ruling Liberal Party, which elected Martin as leader.
On that occasion Bono lauded Martin's promise to sharply increase foreign aid but said he would be keeping a sharp eye on the politician, warning prophetically: "I'm going to be the biggest pain in his ass."
Martin is currently scrambling to keep his minority government alive amid growing anger over a Liberal Party cash-for-favors scandal.
"This is no time to just turn inward. I know there are problems here at home. But don't lose your focus, Prime Minister, on how history will remember this moment," said Bono.