The Treasury Select Committee (TSC) has criticised the Vickers' report on the UK banking sector, arguing its proposed reforms are impossible to assess as they are unclear and lack detail.
MPs said an interim report from Sir John Vickers' Independent Commission on Banking (ICB) failed to properly explain recommendations to ring-fence banks' retail and investment businesses.
The TSC said it found it impossible to properly assess the plans, adding implementing them without further detail would be "a leap in the dark".
TSC chairman Andrew Tyrie said a retail ring-fence would entail "a huge change to the structure of the banking sector in the UK", and debates on the changes must not happen "behind closed doors".
"It is equally important all the information and arguments needed in order to assess the reforms are published by the Committee," he said.
"To implement the ring-fence without having done so would be a leap in the dark. Our long-term prosperity depends on getting this right."
Tyrie said he is concerned about the costs of implementing some of Vickers' proposals, following feedback from the banks.
"The banks warned us the ICB's structural reform options could potentially be costly. They claimed that a retail ring-fence would contribute little to increased financial stability and may inadvertently increase moral hazard and risk-taking," he said.
He urged the ICB to come up with "a more detailed analysis of the costs and benefits of various forms of ring-fence", and "robust" estimates of the cost to the sector and society.
Tyrie also criticised the report for its lack of focus on banks' corporate governance, which he called a "serious omission".
"It must be tackled head on in the final report," he said.
The ICB's final recommendations are due on 12 September.
The body stressed it had not decided whether a full separation of banks' arms, a retail ring-fence, or a more overlooked ‘laisser-faire approach' to banks' structures was the best solution.
It had previously indicated a retail ring-fence was its preferred option, but said in April "much greater detail is required on the work already done on all these options."
The ICB was created in June 2010 to propose reforms for the UK banking sector which would promote financial stability and competition.
Its interim report caused controversy earlier this year when it suggested Lloyds be forced to sell more than the 600 branches it had already agreed with Europe to increase competition, and said banks should be forced to increase their capital buffers to make them more robust.
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