The long-delayed agreement to create a single European patent has this month received a downbeat reaction, with intellectual property (IP) advisers arguing that legal opposition to a European Union-wide patent court will hamstring the venture.

Ministers from 25 EU states on 10 March approved the creation of a single European patent – a unitary title set to operate across much of the EU. The move has been hailed by supporters as a step forward in the decades-long fight to streamline Europe's patchwork patent regime.

IP lawyers, however, have warned the regime will be undermined by an opinion issued on 8 March from the European Court of Justice (ECJ) stating that proposals to create a region-wide patent court conflict with the EU's constitution.

Allen & Overy IP partner Huw Evans said the opinion of the ECJ could delay the widespread adoption of the unitary patent system.

He said: "To some extent the [Council of the European Union's] decision does bring us a little bit closer to having a single EU-wide patent, but there is still the issue of who will oversee the system and who will enforce it – realistically, you simply can't have a unitary EU patent system without having a unitary patent court, too."

Following the Council's decision, a single patent that would be valid throughout all 25 co-operating countries looks set to be created. Italy and Spain have so far refused to back the move after disagreements over the language of the new patent, which looks likely to be translated into only English, French and German.

Supporters argue that the single patent system would boost innovation and create a faster, cheaper and more reliable regime for the creation and enforcement of patents in Europe. The current system requires patents to be validated and translated in each and every member state. According to the European Council, recent studies have shown that obtaining a patent that would be valid in only 13 member states may cost up to ‚Ǩ18,000 (£15,600) – around €10,000 (£8,600) of which would be spent on translations alone.

However, while it is still possible for member states to start working towards a single patent system, IP partners have questioned how significant any changes could be without the creation of a unitary court to enforce it.

The ECJ had quashed hopes for the launch of a single pan-European patent court to oversee any single patent system only days before the Council's decision, stating on 8 March that such a court would infringe on the role of national courts.

Vicki Salmon, a partner at patent boutique IP Asset and a council member at the Chartered Institute of Patent Attorneys, said: "The Council may have given the green light, but the Commission now needs to amend the proposal.† When we see which court will oversee the system, how many member states will want to continue?"

Field Fisher Waterhouse IP partner Joachim Feldges (pictured) said: "The ECJ ruling is a severe setback. It is disappointing, as the current system does not fulfil the needs of a harmonised market and is not future-orientated. The industry needs a more cost-effective and consistent patent litigation system. Now I am convinced that I will be retired before we ever get widespread use of a community patent."

The 25 member states are now waiting for the European Commission to make detailed proposals for the regulations on the unitary patent and on its language regime. The enhanced co-operation agreement will be open to join at any time for those member states which are currently not participating, and businesses from those countries will have access to the unitary patent protection within participating member states.