The editor-in-chief of Bloomberg News said Monday that reporters working for the company's news division should never have been allowed to access otherwise restricted client data.

Allegations surfaced last week that Bloomberg reporters have long enjoyed access to some client data via the company's ubiquitous financial data terminals. The practice was largely unknown outside Bloomberg, and presumably gave the company's reporters an advantage over competitors.

"Our reporters should not have access to any data considered proprietary. I am sorry they did. The error is inexcusable," the publication's top editor, Matthew Winkler, wrote in an op-ed published on Bloomberg's website.

Traders, regulators and central bankers throughout the financial world depend on Bloomberg terminals for real-time data on markets of all kinds as well as news and instant messaging. The machines reportedly rent for $20,000 a year and are used by thousands of subscribers, bringing in a substantial portion of the company's revenue.

Executives at Goldman Sachs (GS) first voiced concern over the surveillance to Bloomberg a few weeks ago after one of the company's reporters spoke to a Goldman executive about the terminal login habits of another Goldman executive.

This prompted concern from Goldman that Bloomberg journalists could be tracking users on the terminals.

Winkler said Monday that the techniques have been used since the 1990s and can be traced to practices that are "almost as old as Bloomberg News."

According to Winkler, reporters could see a user's login history, help desk inquiries and how many times different computer programs were accessed. Other information remained restricted.

"At no time did reporters have access to trading, portfolio, monitor, blotter or other related systems," Winkler said. "Nor did they have access to clients' messages to one another. They couldn't see the stories that clients were reading or the securities clients might be looking at."

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Winkler is the author of "The Bloomberg Way: A Guide for Reporters and Editors" and a member of the Bloomberg LP board of directors. He said the newsroom will no longer have access to the data.

In a memo to Bloomberg employees Friday afternoon, CEO Dan Doctoroff called the newsroom's access to customer data "a mistake."

"Client trust is our highest priority and the cornerstone of our business, and we are deeply committed to ensuring the complete integrity and confidentiality of our clients' data in all situations and at all times," Doctoroff wrote.