IBM has begun a new promotion designed to convert Microsoft Office users to its Lotus Symphony productivity suite.

The company said on Thursday that it will offer the Symphony package along with a collection of plug-ins free of charge.

Microsoft users will be able to obtain the Symphony word processing, spreadsheet and presentation tools for Windows, Mac OS and Linux systems. Large enterprises can also purchase licensing agreements at a discount.

IBM's aggressive new initiative comes as Microsoft faces legal challenges over the lynchpin of its Office suite. Canadian software firm i4i had accused Microsoft of violating its patents on XML components within Word, nearly halting sales of Word in the US.

However, IBM maintains that its campaign is more about advocating Symphony's use of open standards than taking advantage of Microsoft's legal troubles.

"Today there are more innovative, open alternatives such as Symphony that compare favourably to Microsoft Office," said IBM Lotus general manager Bob Picciano.

"Symphony's open collaboration model can offer businesses limitless options cost-effectively at a time when many are increasingly concerned about investing in Microsoft Office."