The Federal Reserve approved the Capital One acquisition of ING Bank, which would make the nation's fifth-largest lender by deposits.

The move goes against the grain of consumer advocates who argued that the merger would create another too-big-to-fail institution.

Netherlands-based global insurer ING is divesting noncore assets as part of an $13.5 billion bailout with the Dutch government. Those assets include $1.6 billion in residential mortgage-backed securities in the United States. The Capital One purchase of ING for $9 billion fits under that mandate.

The approval makes Capital One worth approximately $210 billion, representing approximately 2.3% of the total amount of deposits of insured depository institutions in the United States.

"The board's action directed Capital One to take specific steps to ensure that its risk-management functions, including compliance, are commensurate with its new size and complexity," the Fed said in a statement.

After reviewing the management capacity of Capital One and it financial profile, the Fed board deemed the transaction can reasonably be expected to produce benefits to the public, "such as greater convenience, increased competition, or gains in efficiency, that outweigh possible adverse effects, such as undue concentration of resources, decreased or unfair competition, conflicts of interests, unsound banking practices, or risk to the stability of the United States banking or financial system," the Fed state.

The Federal Reserve board said it also received numerous letter of support for the merger, as well as complaints.