Abstract: The present invention relates to a method and apparatus for obtaining a metal-plastics composite tube. A layer of grafted polyethylene which comes directly into contact with the metal and a layer of cross-linkable polyethylene are extruded simultaneously at least inside this tube, with the aid of an extrusion nozzle having an annular conduit with two distinct coaxial inlets and a single outlet. The invention results in a composite tube having the malleability of lead, the rigidity of copper and a total inertia with respect to the aggressive agents flowing therein.