Opponents of the proposal say Poland's move delivers a serious blow to attempts to make software patentable in Europe.
The Polish government said Tuesday that it could not support the proposed Patentability of Computer-Implemented Inventions that was agreed on by the EU Council earlier this year.
"Because of numerous ambiguity and contradictions respecting the current directive project, Poland cannot support the text which was accepted in the vote of the Council on May 18, 2004," the Polish government said in a statement.
It added that it would be prepared to back a directive that made it clear that "computer-implemented inventions" would be patentable, but that computer programs would not be.
Without the backing of the Polish government, it is likely that the directive no longer has enough support to be sent back from the Council to the EU Parliament. Crucially, the EU has just revised the number of votes that each member state can wield, and this move has given Poland enough influence to tip the balance.
In May, Poland decided to abstain as it did not have enough votes to make a difference. By keeping quiet then, Poland was judged to have supported the directive.
Florian Mueller, a German software developer and campaigner against software patents, believes that the move will force the EU to rethink its position on software patenting.
"I was derided by some when I said on the first of this month that the new voting weights would, because of Poland's position, prevent the EU Council from formally ratifying its May 18 proposal," Mueller said.
"Now that's a reality, and a great opportunity for the Council to properly define the scope of patentability and exclude software," Mueller added.
The Patentability of Computer-Implemented Inventions Directive has caused a storm of protest. Opponents claim that it will allow software to be patented in Europe, and that this will threaten developers and small businesses.
Those in favor of the directive, such as the European Information and Communication Technology Association (EICTA), insist that it would actually maintain the status quo, and help European companies to compete.
Sources at EICTA confirmed Wednesday that the decision of the Polish government to withdraw its support for the directive would be a major setback to its adoption.
"It's not been confirmed to us yet, so we can't say for certain. But we hope it's not the case," said one EICTA employee.
It's possible that another EU country which had previously opposed the directive, or abstained, could still change its position and back it, bringing in enough votes, but the EICTA said that's unlikely.
Graeme Wearden of ZDNet UK reported from London.