Brussels has been accused of an embarrassing gaffe after spending €274 million on a motorway that is set to breach its own environmental laws.

It backed construction of a new road from Sofia to Greece on the understanding it would tunnel under one of Bulgaria’s most-cherished nature sites.

But campaigners say after millions of EU taxpayers’ money was spent on less controversial sections of the road, Sofia scrapped the idea of a tunnel and approved plans to build the road straight through Kresna Gorge.

The gorge has been described as a “unique European treasure” that is home to some of the EU’s most-threatened species.

It is one of the EU’s Natura 2000 sites — a status that aims to protect some of Europe’s most valuable habitats from destruction.

The motorway's route, much of which has been constructed. Credit: Friends of the Earth.

“What Brussels did wrong was not asking the Bulgarian authorities to make sure the gorge was avoided,” said Desislava Stoyanova, a economic and justice campaigner at Friends of the Earth Bulgaria. “But instead they just kept on funding the rest of the motorway.”

Friends of the Earth claims the European Commission said in 2008 that a 13-kilometre tunnel under the gorge was the only way to protect the nature site and that it should be built before the rest of the road.

But, a decade on, other key sections of the motorway have been completed and the Bulgarian government has cancelled plans for a tunnel.

Stoyanova, asked if it was embarrassing for Brussels, said: “Definitely, yes.

“I think it’s important to follow your own values and I would really like to see the EU act as a guardian of EU legislation."

Her comments come after a Bulgarian court last month approved plans for the motorway to pass through the gorge.

The southbound section will expand an existing, smaller road through the nature site and the northbound carriageway will be built some distance away.

Stoyanova says the government has the green light to begin construction and that it is expected to apply for EU funding shortly. It’s unclear if the project would still go ahead without Brussels' cash.

Stoyanova handed a 140,000-signature petition over to the EU's environment commissioner, Karmenu Vella, in Bulgaria on Thursday.

She added: “The Bulgarian government is determined to destroy one of Bulgaria’s most-precious natural jewels, and ruin local communities and sustainable tourism, by cutting a motorway directly through it.

“European law is the Kresna Gorge’s last chance and as custodian of these laws we urgently need the European Commission to act, before the constructors move in.”

Enrico Brivio, a spokesman for the European Commission, said if Bulgaria applied for EU funding to build through the gorge it would be evaluated under the relevant environmental legislation.

“According to the current plans of the Bulgarian authorities, Lot 3.2, which is the only missing link of the motorway, would cut through the area of the Kresna Gorge,” he added.

“This is an environmentally-protected area that belongs to the Natura 2000 network.

“Therefore, when developing Lot 3.2 the legal requirements of the Habitats Directive need to be respected, including in relation to the choice of alternatives with less environmental impact.

“Prior to the issuing of the environmental permit, the project was made subject to a public consultation, in line with the relevant EU legislation.

“The Commission also takes note of the judgment by the Supreme Administrative Court of Bulgaria which finds the environmental impact assessment carried out to be in compliance with the law. This ruling will also be duly taken into account in the Commission’s appraisal.”

Bulgaria’s environment ministry did not immediately respond to Euronews’ request for comment.