Thank you for your answers, but my problem is even worse.
The three inner fiberglass layers of the hull are spongy and the resin used to laminate is sticky. And this is spread over an area of aproximately 3.5 sq meters over the port side of the hull. I'm not sure if I did right, but I already took some of the liner off in order to check the extent of delamination.
By the way, Mallard is a french make. They used to make sailboats, such as mine which is a 9 meter. I think this make still exists, but they don't make sailboats anymore.