Some of the world's biggest banks have been dealing with some of the world's most corrupt regimes, London-based NGO Global Witness said in a report published on Wednesday.

By doing so, the banks had facilitated corruption and looting of natural resource revenues, denying some of the world's poorest people a chance to escape poverty, the organisation said.

"The same lax regulation that created the credit crunch has let some of the world's biggest banks facilitate the looting of natural resource wealth from poor countries," said Gavin Hayman, Global Witness campaigns director.

"If resources like oil, gas and minerals are to truly help lift Africa and other poor regions out of poverty, then governments must take responsibility to stop banks doing business with corrupt dictators and their families," he said.

Undue Diligence

Global Witness's report, entitled Undue Diligence, claims that banks have kept accounts open for dictators' families, despite evidence of the looting of state revenues.

The report also alleges that banks have funded civil wars in Africa.

According to Global Witness, no bank should be, or should want to be, involved in business whose real costs are borne by the people of some of the world's poorest countries.

"Anti-money laundering laws require banks to do due diligence to identify their customer and turn down illicitly-acquired funds, but these laws need tightening to make them globally effective. "

It suggested that banks should change their culture of "due diligence" ? the process by which they check that a customer is legitimate.

"This isn't about box ticking... banks should only take the business if they have identified an ultimate beneficiary who does not pose a corruption risk," the NGO said.

The organisation said that co-operation between governments had to improve to ensure that national bank regulations became globally compatible, accountable and transparent, and were not hindered by bank secrecy laws.

Anti-money laundering regime

"This must begin with reforms to the intergovernmental body that oversees the anti-money laundering regime, the Financial Action Task Force."

Governments had to also ensure that new global rules were put in place to help banks avoid corrupt funds.

The most important change was to ensure that every country produced full public online registers of the ultimate beneficial ownership of all companies and trusts under its jurisdiction, to help banks identify and avoid business with a corruption risk.

"The G20 leaders must act on their promises to help the world's poor... a key element of making poverty history is to stop the money being stolen or kept off-budget in the first place," Hayman said.

"Ducking this issue now leaves the global financial system open not only to further corrupt money flows, but to the destabilising influences that have caused such damage to the developed world's economies," he added.

"The developing world cannot afford a return to business as usual."

In 2003 Global Witness was co-nominated for the Nobel Peace Prize for its leading work on conflict diamonds.