Microsoft went on the offensive Wednesday with a Valentine’s Day attack on IBM openly accusing its rival of trying to subvert Microsoft’s efforts to standardize its new document format and in turn destabilize customer choices.

“A lot of hype -- and smoke and mirrors obfuscation -- surrounds interoperability these days,” Microsoft wrote in an open letter published on its Web site.

The letter was authored by Tom Robertson, the general manager for interoperability and standards, and Jean Paoli (pictured), general manager for interoperability and XML architecture.

The hype and obfuscation references point squarely at IBM, which was the only Ecma International member to vote ‘no’ in December to standardizing Microsoft’s Open XML file format.

Ecma International, an international membership-based standards organization for information and communication systems, approved the standardization measure.

OpenXML is the default file format in Office 2007, and support has been back ported to Office 2003, Office XP and Office 2000.

After the Ecma vote, Bob Sutor, IBM’s vice president of open source and open standards, wrote on his blog: “The OpenDocument Format ISO standard is vastly superior to the Open XML spec.” Sutor also said in his post: “ODF is what the world needs today to drive competition, innovation and lower costs for customers. It is an example of a real open standard versus a vendor-dictated spec that documents proprietary products via XML. ODF is about the future, Open XML is about the past. We voted for the future.”