A tool and method for loosening, for example, a nut connecting an HP rotor to an intermediate housing of a twin-shaft turbojet engine and forward fan including an LP turbine module, an HP module with an upstream journal of the HP rotor, and an intermediate housing with a support bearing of the HP rotor journal. The journal is held in the bearing by the connecting nut. The method includes inserting the tool for loosening the connecting nut after having cleared access to the nut. The loosening tool includes a tube and a plurality of fingers retractable between a position in which they are housed in the tube and a position in which they are deployed radially. The tool is installed with the retractable fingers deployed and in contact with all of teeth of the nut, and an unscrewing rotational torque is then applied to the tool.