Federal Reserve Board members voted on Thursday to adjust key bank regulations put in place after the financial crisis, enacting a series of changes that one board governor, Lael Brainard, warned could weaken “core safeguards.”

Regulators are tying rules more closely to bank size, reducing the necessary level of cash and government bond stockpiles at all but the largest and most complex institutions. Affected banks will also be allowed to submit “living wills” — documents detailing how a bank would wind itself down in the event of failure — less frequently.

Banks with $250 billion to $700 billion in total assets, including firms like Capital One and PNC Financial, will now have to submit a resolution plan every three years, alternating between full and partial filings. They are currently required to submit a full report annually, though in practice they have usually received extensions because the process is so complex. Foreign banks with operations in the United States, including Deutsche Bank, Barclays and HSBC, will also be allowed to file less often.

Ms. Brainard said that while she supported some of the changes approved on Thursday, the overall package went too far.