International banks have ploughed hundreds of millions of euros into a wave of hydropower projects sweeping across many pristine national parks and environmentally-protected regions in the Balkans, according to a new report.

Around half of 1,640 planned and actual projects in countries such as Bosnia, Macedonia and Albania are to be constructed in protected national parks, world heritage and Natura 2000 (EU protected) sites or their equivalents.

The Bankwatch study found that the banks had stumped up at least €818m in 75 projects for which funding could be identified. Thirty of these were in protected areas.

“These sort of projects are going to get renewable energy a very bad name in the Balkans,” said Pippa Gallop, one of the report’s authors.

“Even small hydropower dams can deprive local people of water they need for irrigation. They can stop fish migrating and impact on water quality by turning flowing streams into stagnant bodies of water. Rafters and fishermen can’t use the waterways and neither can animals which relied on the river system as it was.”

In all, conservationists say that 2,700 dams are planned across the Balkans, although the Bern Convention standing committee ordered a stop to one of the most controversial in Macedonia’s Mavrovo national park earlier this month, pending a strategic environmental assessment.

The International Union for the Conservation of Nature had protested to the European Bank for Reconstruction and Development (EBRD) that its support for the $65m project presented “direct threats to critical species,” such as the last 50 or so remaining Balkan lynx in the area.

The EBRD has granted €240m to 51 of the projects named in the Bankwatch report, nearly half of which were in protected areas. Another €36m was provided by the EBRD and European Investment Bank (EIB) for 27 small hydropower plants in the Balkans.

“The EBRD is violating its own policies which are supposed to ensure that all necessary steps are taken to avoid environmentally harmful projects,” Gallop said.

Fierza reservoir, Albania formed as a result of the construction of the Fierza Hydroelectric Power Station. Photograph: Alamy

A spokesperson for the bank said: “The EBRD hasn’t seen the report. However, we are taking the environmental concerns of NGO groups very seriously. We are in touch with Bankwatch and awaiting to see the final version of the report.” But the EBRD’s environmental guidelines pledge not to finance “activities prohibited by host country legislation or international conventions relating to the protection of biodiversity resources or cultural heritage”.

An EIB spokesman told the Guardian that it was sensitive to the issues the Bankwatch report raised. “The EIB recognises the potential contribution of hydropower to renewable energy,” the official said. “As outlined by the EIB’s Energy Lending Criteria hydro schemes need to take account of sensitive safety, environmental and social issues and all hydro projects financed by the EIB have to comply fully with European environmental and social standards.”

Austrian companies stand out as major investors in the report, funding at least 52 greenfield projects, most in conservation areas.

One of these, at Medna Sana in Bosnia has provoked street protests. Ulrich Eichelmann, the director of RiverWatch, an Austria-based conservation group, accused the firms involved of double standards.

“The Sana is the most important river for the globally threatened Danube salmon and they are constructing a dam across its heart,” he said. “They would never be able to do that in Austria.”

The Austrian government has invested €45m in safeguarding national rivers that host the Danube salmon since 1999, according to research by RiverWatch.