Barclays boss Jes Staley is facing a fine after regulators found he had allegedly breached conduct rules by attempting to identify a whistleblower in 2016.
The lender detailed draft warning notices issued by the Financial Conduct Authority (FCA) and Prudential Regulation Authority (PRA), which both allege that Mr Staley's action's violated rules that require an individual "to act with due skill, care and diligence".
However, the bank stressed that regulators are not alleging that the Barclays boss acted with a lack of integrity or that he was not fit to continue in his role as chief executive.
The size of the proposed penalty has not been disclosed.
Mr Staley now has 28 days to respond to the warning notice.
Barclays Bank, which also faced a probe following Mr Staley's attempts to identify the author of the anonymous letter, is not facing any enforcement action by the FCA or PRA.
"However, they have proposed that each of Barclays Bank PLC and Barclays Bank UK PLC will be subject to requirements to report to the FCA and PRA on certain aspects of their whistleblowing programmes," the lender explained.
Barclays said it continues to provide information to and co-operate with US authorities over the incident.
The board said it "continues to have unanimous confidence in Mr Staley" and is still recommending that shareholders back his re-election at the annual general meeting (AGM) on May 1.