A number of large European energy firms and investors are calling on the EU to stop countries undermining investments with retroactive policy changes and tariff cuts.
E.ON, Allianz, Gamesa, RES and Commerzbank are among the companies saying investors are no longer able to rely on EU laws meant to protect them. These laws were previously seen as one of the main attractions to invest in the EU.
In a statement issued by WindEurope, the firms acknowledge regulations need to be adjusted to respond to new technology and changing costs but stress the importance of stable regulations in the long term, especially for renewable energy plants.
They claim Spanish wind energy revenues have fallen by more than a quarter, amounting to €1 billion (£0.88bn) annually, due to retroactive changes introduced in 2012 and 2013.
Investment in Italy is said to have fallen from nearly €13 billion (£11.4bn) in 2011 to €1.4 billion (£1.2bn) in 2015 for the same reasons.
Meanwhile, both Germany and the UK have both rejected retroactive regulatory changes and together account for 67% of total EU renewable energy investment, according to the statement.
The signatories calling on the EU want to see the economic viability of existing projects guaranteed and an international legal system for investors established.