Regional President Valérie Pécresse denigrated a project "whose ecological and economic impact would be disastrous for the towns it crosses, particularly in Yvelines".
According to the motion adopted by regional elected officials, "this line requires the artificialization of hundreds of hectares of agricultural land which is among the best in France."
The project, estimated at 11,5 billion euros by the region, is also an "economic aberration" and "will destroy or damage water resources as well as natural spaces essential to the protection of biodiversity."
Valérie Pécresse had set three conditions for providing her support, particularly financial, to the project: maintaining the stoppage of Normandy trains in Mantois, an extension of the underground section in Yvelines and "that the freight service not be to the detriment of passengers".
All these conditions "were refused by the State and the Normandy region", is written in the motion.
The decision by the Ile-de-France region has sparked anger in the Normandy region and several major urban areas (Rouen, Le Havre, Caen and Cherbourg) which, in a joint statement, described it as "a project of national interest".
"Valérie Pécresse forgets that the project was announced by Nicolas Sarkozy in 2009, and that it was therefore carried out with determination by a government of which she was a member," declared the Normandy communities.
In addition, "the project partners, including its region, have devoted more than 100 million euros to date" to the studies, we can read in the press release.
"A project of national interest cannot be subject to local opposition," write the Normandy region and towns, calling on the State to support the LNPN.
The project, which dates back to 2009, has already passed several key stages. A first phase of study was conducted between 2014 and 2017, and the State reaffirmed "its priority nature" and set a roadmap in 2020, according to the SNCF Réseau website presenting the infrastructure.
The line should connect Paris to Rouen in less than an hour (compared to 1 hour 20 currently) or Paris to Le Havre in 1 hour 45 (compared to 2 hours 05).
The project - which also aims to relieve congestion on the railway lines around Paris - is to develop the existing network, supplemented by the construction of new sections on certain sections, the construction of which is planned for 2035-2040.