The theme was taken up by other senior executives. UBS chairman Axel Weber said regulators risked adding complexity by taking a national approach to new rules on, for example, separating customer deposits from trading activities.

"We want to build a bank of the future, you can't do that if regulation is different - you need a global regulatory standard," he said. Without that, "it will continue to be a complex environment and operational and legal risk will be much higher."

Tidjane Thiam, CEO of insurer Prudential, said achieving a global rulebook would be very difficult to achieve, but that regulators needed to work more closely together to avoid obvious conflicts.

Proposed European solvency rules for insurers, for example, would prevent his company -- a major banking shareholder -- from investing in banks.

"There's a lack of joined-up thinking," he said. "Things are going in all directions.. they are very confused."