The banks and building societies found by the Financial Services Authority (FSA) to be putting their customers at risk of receiving unsuitable investment advice should be identified, according to the Financial Services Consumer Panel (FSCP).
FSCP chair Adam Phillips said the anonymity of the institutions means consumers "are kept in the dark".
Santander has been named as the bank referred to the FSA's enforcement unit following its investigation, though it has not commented on the reports.
The regulator conducted a mystery shopping exercise by making more than 230 undercover visits to six major retail banks between March and September last year.
Among its findings were that, in 15% of mystery shops, the adviser had not properly ascertained the level of risk customers were willing and able to take while, in 13%, the advisers had failed to offer even basic financial recommendations, such as repaying unsecured debt.
The FSCP said more transparency is needed to break the cycle of bank mis-selling.
Phillips said: "We would have expected much better results given the FSA's recent focus on investment advice. These findings are very disappointing. They do however highlight the importance of mystery shopping. Consumers should be entitled to expect more from financial institutions.
"We are keen to see the FSA identify the institutions giving particularly bad advice, not least because the name of one appears to be already in the public domain. The anonymity of these institutions means that consumers are kept in the dark.
"People should be aware of wrongful behaviour and given the opportunity to take their business elsewhere."
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