Mr Cameron attacked a Christian Aid poster that compares free trade to a tsunami, suggesting that it was helping to foster what he called Britain's "cultural hostility to capitalism".
He also appeared to take a swipe at Sir Richard Branson, who put in a bid to run the National Lottery, promising that it would be non-profit-making.
"For too many people, profit and free trade are dirty words," he said. "You can see it when our most popular capitalist entrepreneur thinks the best way to win his bid for the National Lottery is to make it 'non-profit'. You can see it in the Christian Aid poster that compares free trade to a tsunami."
But Christian Aid retorted that Mr Cameron's "ill-advised gibe" had completely missed the point of its campaign.
"Christian Aid is not anti-free trade and we have no objection to profit," a spokesman said.
"What we do say is that the way that trade rules have been stacked against poorer countries is neither 'fair' nor 'free' and that developing nations should be entitled to the same measure of protection that developed countries employed on their way to becoming rich.
"We make the comparison with the tsunami to highlight the sad fact that somewhere in the world a child dies needlessly of poverty-related diseases every three seconds."
Mr Cameron delivered the longest speech yet in the long-running Tory leadership contest, addressing the big issues of handling public finances and eliminating world poverty.
He claimed that the root cause of recent troubles like the riots in the Lozells area of Birmingham was the "shackles of poverty", which made it hard for people in such areas to start up new businesses.
The same problems were found in the Third World, where they were compounded by the absence of a legally protected system of property rights, he said. He suggested setting up a property rights fund to help protect local businessmen in the Third World.
"We see two distinct economic challenges - thwarted growth alongside stubborn poverty, two sides of the same economic coin," he said. "But for many years we Conservatives have focused too much on one - the thwarted growth. Creating wealth cannot be the only objective of Conservative economic policy."
Kate Green, chief executive of the Child Poverty Action Group, said: "Mr Cameron is right to talk about freeing people from the shackles of poverty, but he needs to explain what he would do to achieve this.
"Compassionate conservatism may be a good soundbite but without a well-thought out approach to tackling the causes and consequences of poverty, David Cameron risks being accused of empty rhetoric."
His rival David Davis concentrated on how to organise the Conservative Party - an issue that might not mean much to most voters, but matters to the 300,000 party members who will be receiving their ballot papers in the next few days.
His proposals included paying people who are selected as parliamentary candidates in seats which the Conservatives are particularly keen to win.
Mr Davis proposed setting up a trust fund to subsidise candidates in such key seats.
He said: "I know what a big commitment being a candidate is. Not just mentally, emotionally and physically, but also financially.
"I fear that it is such a huge financial commitment that we are losing out on some great candidates who cannot afford to be selected early in a parliament for fear of what it will cost them. We cannot afford to lose some of what could turn out to be our best candidates."
Mr Davis also suggested holding future party conferences in a big city rather than at a seaside resort.
Today the two contenders will go head to head in a pitch for the votes of Tory women. They will each make a short speech and answer questions.
Both will also appear on BBC Radio 4's Woman's Hour programme.Reuse content