The move follows a previous decision to offer government's access to Windows source code and Microsoft Office 2003 XML Reference Schemas announced last year.
The Redmond giant explained that its Government Shared Source Licence for Office will give qualifying national governments and international organisations access to Office 2003 source code and technical information - boost security and interoperability between Windows and Office products.
"The release of this source code will help the UK Government understand the security implications of the Office productivity suite and aid secure deployment in a wide range of scenarios," said Dr Steve Marsh, director of the Central Sponsor for Information Assurance in the Cabinet Office.
"Microsoft's collaborative approach and source-code access have demonstrated a deeper level of commitment to our ongoing collaboration."
Introduced in January 2003 as an extension of the Microsoft Shared Source Initiative, GSP is a no-fee global programme designed to promote increased communication and collaboration between government customers and Microsoft.
The programme gives access to Windows 2000, Windows XP, Windows Server 2003, Windows CE and Office 2003 source code, along with additional documentation, and training and technical engagements
To date, more than 30 countries, including Australia, China, Norway, Russia, Spain and the United Kingdom, have signed GSP agreements, according to Microsoft.
"At Microsoft, we view governments that utilise our software as trusted partners. The addition of Office 2003 to the GSP demonstrates our continued commitment to collaborating with governments all over the world to deliver solutions that address their unique and specific IT needs," said Jonathan Murray, vice president and chief technical officer of Microsoft EMEA.