Addressing policymakers in Davos, Cameron said the questions of fairer taxes, more open trade and greater transparency apply just as much to the developed countries of the G8 as to poorer nations.

And he dismissed the idea that speaking out on the issue of taxes and transparency made him anti-capitalism or anti-business.

Poor practice by some firms has an impact on those that play by the rules, he said.

There is a difference between tax evasion and tax avoidance, he added, "but there are some forms of avoidance (that) have become so aggressive that I think it is right to say these raise ethical issues, and it's time to call for more responsibility and for governments to act accordingly."

"I'm a 'low tax' Conservative but I'm not a 'companies should pay no tax' Conservative," added Cameron, who heads Britain's Conservative Party.

Meanwhile, transparency about the flow of money is key to poorer countries moving from poverty to growth, Cameron said.

"Like everything else in this G8, the ambitions are big, and I make no apology for that," he said. "We can be the generation that eradicates absolute poverty in our world," he said, but only if leaders focus on the cause, not the symptoms.

CNN's Richard Quest said Cameron's attempt to go after tax cheats could be seen as good populist politics and an easy shot as he tries to distract from other matters.

No cherry-picking

On Wednesday, Cameron promised that if his party wins the 2015 general election, the country would get to vote on whether Britain stays in the European Union on the basis of a renegotiated deal, or leaves.

The referendum should not be held until it's clear how changes made after the crisis in the eurozone works out, he said, but will be held in the first half of the next parliament.

The long-awaited speech was met with approval by those in his party who want to see Britain get some powers back from the EU, as well as a reduction in legislation they say holds back businesses.

But critics -- including his party's coalition partner, the Liberal Democrats -- say now is not the time to create uncertainty among businesses and industry over Britain's future in the European Union.

It is also unclear whether the other 26 members of the European Union would be willing to renegotiate the terms of Britain's membership.

France and others have made it clear that the British leader cannot "cherry-pick" which elements of the EU he signs up to, or risk unraveling the union to suit British interests.

U.S. President Barack Obama has also said that "the United States values a strong UK in a strong European Union."

But German Chancellor Angela Merkel gave Cameron some room for maneuver, indicating she is open to discussions on a "fair compromise."

She is also due to give a speech Thursday at Davos, the annual forum that this year is attended by nearly 40 world leaders and more than 2,000 executives.

Italian Prime Minister Mario Monti, speaking at Davos Wednesday, predicted Britain would remain in the EU.

"I am confident that if there is to be a referendum one day, the UK citizens will decide to stay in the EU and contribute to shape its future," he said. He added, however, "I think the EU does not need unwilling Europeans."

Britain is a net contributor to the European Union and an important player in the single market, which may give Cameron some additional sway. But critics warn he is taking a big gamble.

Former Belgian Prime Minister Guy Verhofstadt, who leads the Alliance of Liberals and Democrats for Europe in the European Parliament, warned against trying "hold the EU to ransom."