The blueprint regulators gave Barclays Plc and other banks for correcting Libor-rate abuses may not be enough to salvage a benchmark so discredited it needs to be overhauled.

The U.S. Commodity Futures Trading Commission ordered Barclays on June 27 to keep thorough records on how it comes up with its London interbank offered rate submissions and erect so-called Chinese walls between traders and rate-setters. It also said lenders should expect random checks from regulators on whether their submissions reflect actual borrowing costs. Investors say the plans are little more than window-dressing.

"As long as banks are allowed in the henhouse, then the system is ripe for abuse," said Tim Price, who helps oversee more than $1.5 billion at PFP Group LLP, an asset-management firm based in London. A better system would be to take random samplings from all the transactions, he said. "If there is any message of the last few years, it's that banks and bankers simply cannot be trusted."