The Dutch government has set a soft deadline of April 2008 for agencies at the national level to adopt open-source software such as free word processing programs and Internet browsers, the Economic Affairs Ministry said Thursday.

Under the policy, approved Wednesday, government organizations will still be able to use proprietary software and formats, but will have to justify that decision under the principle of ''adopt or explain'' why not, ministry spokesman Edwin van Scherrenburg said.

Van Scherrenburg said the plan had been approved unanimously at a meeting of two parliamentary commissions Wednesday.

Many governments worldwide have begun testing open-source software to cut costs and eliminate dependency on individual companies such as Microsoft Corp. -- or at least expressed interest in the idea -- but the Dutch have been among the most aggressive in taking action.

Notably, the policy directs government organizations at the national level to be ready to use the Open Document Format, or ODF, to save text files by April, and at the state and local level by 2009. It also says that governments should prefer open-source software and files, all things equal, whenever possible.

Van Scherrenburg said the government estimates it would save euro6 million (US$8.8 million) annually on city housing registers alone due to a switch to the ODF standard.

Microsoft has raced to achieve ''open source'' certification for its Open Office XML standard, but has so far failed to receive endorsement from the International Standards Organization, the certifying authority recognized by the Dutch government.

Microsoft Netherlands spokesman Hans Bos noted that its Word documents were still allowed as equal alternatives to ODF for the moment, and added he expects the company will soon receive approval for its Open Office XML to qualify as ''open source.''

But he said the company was worried about and opposed other aspects of the Dutch policy.

Specifically, he said, the provision that government agencies should prefer open source was overly proscriptive.

''We think it's not in the best interest of the wider software market to single out one model for endorsement like this,'' he said.

In addition, he said the strict technical definition the Dutch government is using to define ''open source,'' if enforced, would prevent governmental bodies from using many industry standards that are useful.

''For instance, it would prohibit the use of GSM, Wifi, Mp3, Mpeg2, Mpeg4 and Bluetooth -- all widely accepted standards, but proprietary and licensed,'' he said.

Economic Affairs Minister Frank Heemskerk also announced plans Wednesday for a Project Bureau -- the equivalent of a tech support desk for agencies adopting new open-source software -- and for a new agency that will check up on whether government bodies are following the directive.

The City of Amsterdam has been carrying out a test of a complete switch to open-source software, including using Linux-based operating systems on all computers, in its housing department and one of its borough offices, Zeeburg.

Numerous other European towns and cities, notably Munich, Germany, and Vienna, Austria, have switched partially or mostly to open-source systems but they remain a tiny slice of the overall market.