As federal regulators move toward adopting a final version of their 298-page proposed rule to restrict proprietary trading by banks, plenty of critics are warning about the unintended consequences to the financial markets that they say the Volcker Rule will inflict.

In comment letters to the Securities and Exchange Commission and other federal agencies, executives at financial firms and their representatives have argued that the Volcker Rule will send harmful shock waves through the financial sector.

“We are concerned that the approach taken by the financial regulators … poses significant impediments to our ability to effectively and efficiently manage our ...