process for manufacturing a fuel tank equipped with an internal accessory and having a plastic wall produced from a parison , the process including , in order , the following steps : a ) the accessory and the molten parison are introduced into a mould so that the accessory is surrounded by the parison , the mould including cavities equipped with at least one moving part ; b ) a pressurized gas is introduced inside the parison to carry out a pre - blow moulding of the parison ; c ) the pre - blow - moulded parison is pressed locally against the accessory using the moving part in order to firmly attach the two without piercing the parison ; d ) the mould is closed and the final blow moulding of the parison is carried out by flattening it against the mould cavities using the pressurized gas ; and e ) the tank is removed from the mould .