The directive on "Patentability of Computer Implemented Inventions" has been a subject of hot debate among the EU institutions and other experts since 2001.

This week's vote is part of the second-reading in parliament, which should lead to a final decision by member states on the legislative piece.

The main dispute concerns the extent of protection that should be granted to computer-driven inventions, such as car brakes, washing machines or cell phones.

Large companies argue that computer programmes themselves should be patented, not just the individual inventions they relate to.

Major European firms like Nokia, Ericsson, Siemens, Philips and Alcatel have warned that billions in research and development spending would be wasted if they were denied access to patent protection.

But small and medium sized businesses (SMEs) insist that software should be excluded from the scope of the directive, suggesting it is sufficiently covered by the exitsing copyright system.

While registration for copyright application is relatively cheap, patent procedures cost between €10,000 euro in the US and €50,000 in Europe.

Opponents of the law are concerned that the new directive will move Europe towards the US system of giving patents for Internet business models such as online bookseller Amazon's one-click shopping technique.

Strong lobby

The software patent directive has seen mixed fortunes in recent months.

In March, member states agreed on a common position despite a unanimous call by the leaders of all of the parliament's political groups for its withdrawal.

The common position then received the backing by the parliament's legal committee in mid-June, leaving the draft based on the idea that patent protection should generally extend to computer programmes as advocated by big software companies.

The Socialist, Greens and the left-wing GUE/NGL groups are now expected to back the reintroduction of restrictions on patent protection to inventions.

On the other hand, MEPs from center-right and liberal groups are set to reject the amendments by the Socialist rapporteur and vote in favour of the member states' position.