Reform of Britain's banks should go further to ensure a total ring-fencing of their retail and investment arms, a government commission set up after the Libor scandal said in its first report on Friday.
The chairman of the Parliamentary Commission on Banking Standards, Conservative lawmaker Andrew Tyrie, said the ring-fence needed to be "electrified" for it to be effective.
The government has published draft legislation to ring-fence retail banking and the more risky investment banking arms by 2019 in a bid to avoid taxpayers having to bail out troubled banks as was the case during the financial crisis.
But Tyrie said "the proposals, as they stand, fall well short of what is required".
"For the ring-fence to succeed, banks need to be discouraged from gaming the rules. All history tells us they will do this unless incentivised not to," he added.
"That's why we recommend electrification. The legislation needs to set out a reserve power for separation; the regulator needs to know he can use it."
The commission's concerns put it at loggerheads with finance minister George Osborne, who last month urged it not to "unpick" a consensus on structural reform of the banking sector.
The parliamentary commission was set up in the wake of revelations earlier this year that Barclays tried to manipulate the Libor rate, which is used as a benchmark for global financial contracts worth about $300 trillion.