Antonio Maria Costa of the UN Office on Drugs and Crime said he had collected ample evidence to make such accusations.
"Consultations I've had with prosecutors and law-enforcement officials around the world show there is ample evidence that the banking system's illiquidity is providing a unique opportunity for organised crime to launder their money," said Costa.
"Just about every financial centre can be characterised as part of the problem," Costa said in the interview, but declined to name countries or banks involved, saying that was for prosecutors and other law-enforcement bodies to do.
Costa said a Vienna conference next month marking the 10th anniversary of a UN General Assembly special session on drugs would mull ways to boost steps against money laundering and ease the impact of drug gang profits on the integrity of states.
He said the multilateral Financial Action Task Force (FATF) formed in 1991 did much to help drive mafia money out of banks over the ensuing decade but that achievement was being challenged by the global haemorrhaging of legitimate credit.
"You have the supply -- an organised crime industry with enormous amounts of cash, estimated at $322 billion in 2005, not any more stored in banks -- and the demand, a banking sector strapped for liquidity," said Costa.
"This is a supply- and demand-driven situation. Our intuition, based on logic, is now supported by ample evidence."
Asked where cases were occurring, he said: "Traditionally, Europe and North America are the places where, as financial centres, most money would be laundered.
"What we are seeing," Costa said, "is the weakening of the strongest instrument embedded in the FATF campaign, and that is, 'Know your client'. That is, accept resources only from those you know, and if you don't do so, inform the authorities.
"It has been quite widely documented that because of the difficult financial situation of banking institutions, that principle has been weakened to the point of being indirect evidence of what we are (talking about)." Costa said many member states in his UNODC agency were saying the time was not yet right for additional measures against money launderers taking advantage of struggling banks.
"I insist that the (globalised) crime industry has become so gigantic, destabilising so many countries, that it is emerging in areas where we have not seen it before. They're buying more than just industry, real estate, elections, power," he said.
"We will present some concepts and lines of action for member states to consider when ministers meet next month, related to the size and shape of organised crime and the threat it is now posing."
Costa raised the appearance of links between the liquidity crunch and organised crime cash flows at a closed gathering of financial industry professionals in Frankfurt in November.
Britain said in December that financial sector fraud had risen alarmingly, fifteen-fold, since its credit markets began seizing up but was typically committed by internal managers and suppliers rather than organised crime.