Amec withdrew from the project in March, saying the scheme was not commercially viable. However, the consortium to build the dam is led by French contractor Spie. Amec owns 46% of Spie and is expected to buy it outright later this year.
Friends of the Earth spokesperson Hannah Griffiths said: "If it's not viable for Amec, why is it for Spie? As far as we're concerned, this campaign is not over."