British prime minister David Cameron has called for international action to fight tax evasion and avoidance and improve business transparency.
At the annual World Economic Forum in Switzerland on Thursday, Mr Cameron said although technology has made the world more open, some financial practices remain closed and secretive.
"Individuals and businesses must pay their fair share," he said in Davos. "Trade, tax and transparency" were Britain's economic priorities.
Mr Cameron said that cutting down on tax avoidance was one of Britain's main priorities for its presidency of the G8 group this year.
"There are some forms of tax avoidance that have become so aggressive" that it is time for international co-operation to make sure that global companies pay their fair share of tax, he said.
"This is a problem for all countries, not just for Britain," he said.
"Acting alone has its limits. Clamp down in one country and the travelling caravan of lawyers, accountants and financial gurus just moves on elsewhere. So we need to act together at the G8."
Tax evasion is illegal, but tax avoidance is legal.
Much of the debate about what is fair to pay is over "transfer pricing", which involves payments from companies to each other within the same corporate structure. The BBC reports that what often happens is that the taxable profit is shifted somewhere else - where taxes are usually much lower.
The BBC also reports the prime minister defended his decision to offer a referendum on Britain's membership of the European Union after 2015, if the Conservatives win the next election, and said that the bloc needed to change.
Europe is being out-competed, out-invested and out-innovated," Mr Cameron said.
