LONDON—The Bank of England rebuffed calls for stronger oversight of the interest-rate benchmark at the center of a global scandal, according to a trove of internal emails and documents released Friday.

The disclosures are likely to intensify a debate over whether the central bank in past years did enough to defuse a brewing crisis involving banks' attempted manipulation of the London interbank offered rate, or Libor. Top Bank of England officials have said they didn't act more aggressively partly because they were unaware...