A former Goldman Sachs banker suspected of taking confidential documents from a source inside the government has agreed to plead guilty, a rare criminal action on Wall Street, where Goldman itself is facing an array of regulatory penalties over the leak.

The banker and his source, who at the time of the leak was an employee at the Federal Reserve Bank of New York, one of Goldman’s regulators, will accept a plea deal from federal prosecutors that could send them to prison for up to a year, according to lawyers briefed on the matter who spoke on the condition of anonymity. The men, both fired after the leak, also may face lifetime bars from the banking industry.

In a statement, a Goldman spokesman emphasized that the banker worked for the firm for less than three months, and that the bank “immediately began an investigation and notified the appropriate regulators” once it detected the leak. Nonetheless, the bank is expected to pay a significant penalty.

Under a tentative deal with New York State’s financial regulator, the lawyers said, Goldman would pay a fine of $50 million and face new restrictions on how it handled delicate regulatory information. The settlement with the Department of Financial Services would also force Goldman to take the rare step of acknowledging that it failed to adequately supervise the former banker — thrusting the bank back into the spotlight just as it was beginning to overcome a popular image as a firm willing to cut corners to turn a profit.