A process for producing a container comprising an outer container, an inner bag disposed therein and a pressure equalisation opening disposed in the outer container, and a container produced according to this process, is described, wherein a pre-moulding, comprising two coaxial tubes, is first produced by co-extrusion with the help of a blow mould and with an outwardly-projecting base seam being formed. The process forms a pressure equalisation opening in the outer container without endangering the integrity of the container, wherein a lower wastage rate and higher productivity are achieved. To do this, the base seam is partially cut off and a force which acts in the direction of the seam is introduced into the pre-moulding, which has a temperature of 40 degrees C. to 70 degrees C., which force breaks open and plastically deforms the base seam so that a pressure equalisation opening is formed in the base area.