Bill Clinton: America should lead the way against Aids. Photograph: Ronald Zak/AP

Bill Clinton and Bill Gates called for better use of the money donated to fight Aids as the world economic crisis makes an increase in funding unlikely.

In a speech to the International Aids conference in Vienna, Gates, the chairman of Microsoft and one of the world's biggest philanthropists, called for a fresh focus on efficiency and initiatives that are known to work.

"This is a tough economic environment. Right now there isn't enough money to simply treat our way out of this epidemic," he said.

"If we keep spending our resources in exactly the same way we do today, we will fall further behind in our ability to treat everyone."

Gates cited male circumcision, which a major trial four years ago showed could reduce the chances of a man contracting HIV by 60% – although it is as yet not proven to protect women.

This and giving a short course of drugs to mothers and their newborn babies to prevent the child becoming infected were, said Gates, "so cheap and so effective that in endemic countries it is more expensive not to pursue them".

Clinton, a former two-term US president, called for better use of the limited funds available in a separate speech warning that excessive resources went on bureaucracy, unnecessary trips and unread reports.

"In too many countries, too much money pays for too many people to go to too many meetings and get on too many aeroplanes to do too much technical assistance," he said. "Too much money is spent on reports that sit on shelves. Every dollar we waste a day puts a life at risk."

He called on America to lead the way and for all countries "to do some soul-searching … and actually spend the money on the people it was meant to help instead of the apparatus in the country in question".

Clinton said he did not want to blame anybody. "I was president for eight years and I had no idea it was as bad as it was," he said. But, he added: "We can fix this."

Anil Soni, chief operating officer of the Clinton Foundation, said there had been an understandable tendency for donors to turn to organisations in Washington or London with expensive overheads. "Those are wonderful, but they should never be who we are relying on for most of the delivery of care," he said.

Clinton suggested to the conference, where more than 20,000 delegates have gathered, that protests against Barack Obama's failure to spend more money on Aids, which have been taking place in Vienna, were not the best way forward. Obama has been criticised for not increasing Aids funding while refocusing his global health initiative on cutting deaths of mothers and babies and strengthening basic healthcare systems in the developing world.

But Clinton argued that lobbying the White House was more likely to pay off than demonstrating against it.

Dr Zeke Emanuel, a White House health policy adviser, denied activists' accusations that the US administration was backing off its commitment to Aids. "There are no cuts, no rollback, no shrinkage in what we are funding," he told the Guardian.

Washington contributes more than half the funds that go to global health.

"Where many countries cut back in 2008-09, the government increased its expenditure by over 10%. This idea is nonsense – it's just a canard," Emanuel said.

The Obama administration's budget request for 2011 increased Aids funding by 2.5% and that for global health by 8%, he added.