Push-in tube connector port for connecting a tube to a pressurized fluid system, the tube connector port comprising a central recess for receiving an end portion of the tube, said recess having an insertion end opening and an abutment end for delimiting the maximum insertion depth of the tube in the recess, a sealing arrangement inside of the recess including an environmental sealing ring and further inside the recess a main sealing ring, the main sealing ring being configured to prevent fluid from flowing out of the tube into the recess when the tube is inserted into the recess, a locking ring engaged within the recess and engaging the environmental sealing ring to retain the sealing arrangement inside of the recess and to prevent it from being blown out of the recess, and a tube gripping ring having an inwardly directed gripping edge and being located closer to the abutment end of the recess than the sealing arrangement, the tube gripping ring being configured to cooperate with a conical wall portion in the recess for delimiting its movement towards the insertion end opening for compressing it upon such movement to thereby urge its gripping edge further towards the tube to thereby prevent the tube from being pulled out of the recess, characterized in that the recess comprises an inwardly projecting circumferential flange at the insertion end opening of the recess, and in that the locking ring comprises an annular double ring component formed by a profile of elastic plastic material having a U-shaped cross-section forming an inner ring wall and an outer ring wall connected to each other by a bottom wall portion of the U-shaped cross-sectional profile, wherein a number of circumferentially distributed slots subdivides the outer ring wall into a number of outer ring wall portions configured to be elastically deflected towards the center by the flange of the insertion end opening, when the annular double ring component is pressed into the recess, and to elastically flex back outwardly once the outer ring wall portions have passed the flange such that an upper edge of each of the outer ring wall portions engages an inner surface of the flange to secure the locking ring in the recess. a central recess for receiving an end portion of the tube, said recess having an insertion end opening and an abutment end for delimiting the maximum insertion depth of the tube in the recess, a sealing arrangement inside of the recess including an environmental sealing ring and further inside the recess a main sealing ring, the main sealing ring being configured to prevent fluid from flowing out of the tube into the recess when the tube is inserted into the recess, a locking ring engaged within the recess and engaging the environmental sealing ring to retain the sealing arrangement inside of the recess and to prevent it from being blown out of the recess, and a tube gripping ring having an inwardly directed gripping edge and being located closer to the abutment end of the recess than the sealing arrangement, the tube gripping ring being configured to cooperate with a conical wall portion in the recess for delimiting its movement towards the insertion end opening for compressing it upon such movement to thereby urge its gripping edge further towards the tube to thereby prevent the tube from being pulled out of the recess, characterized in that the recess comprises an inwardly projecting circumferential flange at the insertion end opening of the recess, and in that the locking ring comprises an annular double ring component formed by a profile of elastic plastic material having a U-shaped cross-section forming an inner ring wall and an outer ring wall connected to each other by a bottom wall portion of the U-shaped cross-sectional profile, wherein a number of circumferentially distributed slots subdivides the outer ring wall into a number of outer ring wall portions configured to be elastically deflected towards the center by the flange of the insertion end opening, when the annular double ring component is pressed into the recess, and to elastically flex back outwardly once the outer ring wall portions have passed the flange such that an upper edge of each of the outer ring wall portions engages an inner surface of the flange to secure the locking ring in the recess.