The principle of matching pay to risk “has proven to be challenging” the Basel Committee on Banking Supervision said in a statement on its website today. “As of October 2010, effective implementation” of such bonus practices “has not been achieved,” said the committee, which last month proposed tougher capital rules for banks worldwide.

Lawmakers and regulators are reviewing bonuses to avoid a repeat of the excessive risk-taking that led to the worst financial crisis since World War II. The Committee of European Banking Supervisors last week said that bankers should be able to get a maximum of a quarter of their bonus in an immediate cash payout.

Banks should defer share awards to employees for “a sufficiently long” time “to ensure that appropriate incentives are built” and to “truly differentiate” the shares from a cash payment, the committee recommended.

Regulators are still grappling with “the best feasible way” to control guaranteed bonuses for new employees, the committee, based in Basel, Switzerland said. This “remains an open question.”

Limits on cash bonuses and “timelines of payouts in themselves do little to curb individual incentives for excessive risk-taking though they are steps in the right direction,” Sony Kapoor, managing director of policy think-tank Re-Define Europe, said in an e-mail.

“Risk-Takers”

The Basel committee said that rules forcing bankers to pay back their bonuses if the lender experiences a financial crisis should apply to all “material risk-takers” in a bank, not just “senior executives or traders.”

“These could be either individual employees or groups of employees who may not pose a risk to the financial soundness of an institution on an individual basis,” the report said.

The Basel Committee, which is made up of bank regulators from around the world, reached an agreement Sept. 12 for rules that more than double capital requirements for banks, while giving them as long as eight years to comply. Germany had sought to give firms a decade to make the transition, while the U.S., U.K. and Switzerland pushed for a maximum of five years.

“The industry has already implemented” proposals on pay endorsed by leaders of the Group of 20 nations, Rob McIvor, spokesman for the Association for Financial Markets in Europe, said in an e-mail.