A container has a peripheral wall defined by a single preformed blank of flexible sheet material and provided with axially extending injection moulded ribs, one of which forms a seam uniting juxtaposed opposite edge portions of the piece of flexible sheet material, and at least one circumferentially extending injection moulded rib. One end of the zone bounded by the peripheral wall is closed by an end closure formed of injection moulded material or flexible sheet material. The container is formed in a container shaped mould cavity which constrains the sheet material to the required shape while the ribs and end closure are being injection moulded simultaneously.