The call comes as France's prime minister Edouard Philippe is expected to make a decision in the coming days about the future of the six projects totaling 3GW awarded in 2012 and 2014.
Concerned about the cost of state support for the projects, in March the government introduced an amendment to a bill allowing it to renegotiate the tariffs, or even cancel the projects altogether.
Although the amendment was defeated, the government says it wants to stick to its goal.
The three organisations called for talks with the developers to be reopened "as quickly as possible", particularly regarding the purchase price.
According to SER, the agreed tariffs average €190/MWh for the six projects, excluding grid connection.
It estimates "real cost" of government support will amount to €12.4 billion, well below the €40.7 billion quoted by regulator CRE in 2017.
At the same time, SER points out that the projects — Courseulles-sur-Mer, St-Nazaire, Fécamp, St-Brieuc, Dieppe-Le Tréport and Les Iles d'Yeu et Noirmoutier — represent the corner stone of French ambitions to launch an offshore industry, promising to create over 15,000 jobs.
This would help compensate the cost of state support. "The economic spin-offs related to industrial plans (excluding direct taxation from operation) would be ... of the order of €5 billion for all six projects," SER estimates.
Calling the projects into question "would seriously undermine the attractiveness of [France] for investors and generate major legal issues," Jean-Louis Bal, president of SER, said.