Plans to build a motorway through a protected nature reserve were thrown into disarray last night when the European Commission launched a last-minute legal challenge to thwart the project, which is part funded by the EU.

Work was due to begin on a 17km (11mile) stretch of road through the Rospuda Valley in northeastern Poland tomorrow, as part of a planned motorway to link Warsaw to Helsinki via the Baltic states.

However, the Commission insists that the road would cause irreversible damage to one of Central Europe’s finest natural habitats, comprising ancient forest, peat bogs and rare flora and fauna.

It announced that it had asked the European Court of Justice to intervene. The case is expected to be the first of a number of environmental disputes as Eastern European members modernise their roads and railways. The motorway would mark the first time that a member state had proceeded with an infrastructure project in defiance of an EU order.

“It is regrettable that Poland has now decided to go ahead with the construction of a new road through Rospuda Valley,” Stavros Dimas, the EU Environment Commissioner, said.

“I would hope that Poland will reconsider its decision before irreparable damage is done. In the meantime, the Commission has asked the Court of Justice to issue an injunction to maintain the integrity of the site,” he added.

Jerzy Polaczek, the Polish Transport Minister, called the Commission’s decision bizarre and said that the Government would study the complaint before making a final decision, but was ready to go ahead as planned. “Work on the construction is currently being completed in accordance with the contract,” he told reporters.

Construction of the road, a section of the Via Baltica linking Poland and Finland was suspended in March because of the bird-nesting season. The Rospuda Valley has been designated as a protected area for wild birds and is part of the EU’s Natura 2000 network of protected nature sites.

“The valley contains a rare mosaic of unspoilt habitats within one of the largest and best-maintained primeval forests in Central Europe,” the Commission said. Warsaw wrote to the Commission last week, refusing to promise that construction work would remain suspended.

Barbara Hellferich, a Commission spokeswoman, said that it would be unprecedented for a member state to go ahead with such work in defiance of an EU order.

“This is uncharted territory. We have not had a case like that before,” she said.

The Commission wants the work halted until the court delivers a final verdict on whether the motorway construction in the area is compatible with strict EU environmental laws.

Thijs Berman, a Dutch Member of the European Parliament, said: “The development of the Via Baltica strategic road network in Central and northeast Europe is essential to the economic and social cohesion of the European Union as a whole.

“But an even higher priority should be given to better rail links in the area because of their long-term benefits. The choice is largely a question of member states’ policies but the European Union would encourage rail over road.”

The European Commission brought the Via Baltica case before the Court of Justice in March, claiming a breach of EU environmental protection laws. Mr Berman said: “The Polish authorities have failed to show that they examined alternatives to the current road construction project properly and objectively.”

Commission officials say that building the motorway through the valley could compromise EU funding for the whole Polish stretch of the planned motorway, which could amount to hundreds of millions of euros.

The section of the motorway through Rospuda is to be built without EU funds. But Poland hopes that Brussels will help to fund construction of other parts of it.

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