The appeal comes a week after the Guardian newspaper reported that Microsoft allowed U.S. security agencies to circumvent encryption of Outlook emails and capture Skype online chats, citing leaked documents provided by Edward Snowden.
The world's largest software company said there were "significant inaccuracies" in the media reports last week and asserted it does not allow any government direct or unfettered access to customers' emails, instant messages or data.
In a letter to Attorney General Eric Holder made public on Tuesday, company lawyer Brad Smith asked Holder to take action personally to permit Microsoft to reveal more about how many security requests it receives and how it handles them.
"We believe the U.S. Constitution guarantees our freedom to share more information with the public, yet the Government is stopping us," said Smith in a blog on Microsoft's website.
He said government lawyers have not responded to a court motion made in mid-June asking for permission to publish the volume of requests it has received.
So far, the U.S. government has restricted what companies can say under about the requests under the highly secret Foreign Intelligence Surveillance Act. Last month, it allowed the disclosure of aggregate numbers of requests for customer data, but not the breakdown of the split between surveillance and crime-related requests.
Microsoft and Google Inc., along with Apple Inc., Facebook Inc. and other U.S. tech leaders are scrambling to assert their independence after documents leaked to the Guardian suggested they gave the U.S. government "direct access" to customer accounts as part of a National Security Agency (NSA) program called Prism.
The Guardian went further in detailing Microsoft's collusion with the NSA last week, citing new top-secret documents it said were leaked by Snowden, the original source of the Prism reports.
Microsoft did not directly mention the latest Guardian report, but contradicted its central claims.
"Microsoft does not provide any government with direct and unfettered access to our customers' data," said Smith in his blog. "Microsoft only pulls and then provides the specific data mandated by the relevant legal demand."
(Reporting by Bill Rigby; Editing by Gary Hill and Andre Grenon)
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