An inspection method for detecting leaks in a vacuum bag assembly used in the manufacture of a composite part, the method comprising spraying helium over the surface of the vacuum bag and using a suitable helium detecting equipment to detect helium dragged by the vacuum inside the vacuum bag through a leak; - the vacuum bag assembly comprising a cured panel, a plurality of uncured stiffening stringers, curing tools (21, 21') for the uncured stiffening stringers with fastening clamps and a vacuum bag arranged directly over the composite part; - the vacuum bag being formed joining individual bags for the uncured stiffening stringers and other bag pieces (25, 26) to cover the whole panel; the inspection method comprising the following steps: - creating a local helium atmosphere over the vacuum bag assembly by zones following a programmed zonal sequence for a first leak detection test of each zone (Z j,j); the local helium atmosphere being created inside a chamber placed over each zone (Z j,j); the zones of the vacuum bag assembly to be covered by said chambers are set so that in the direction of the stiffening stringers have a predetermined length and in the direction transverse to them comprise, for each stringer, the space occupied by its individual bag, being a sealing tape of two contiguous individual bags assigned to the zone of one of them so that it can be covered by one chamber; the first leak detection test giving a positive result when the helium detected by the helium detecting equipment inside the vacuum bag exceeds a predetermined first threshold; and - if the first leak detection test gives a positive result in a particular zone (Z j,j), creating a new local helium atmosphere over the zone (Z i,j) for a second leak detection test; the second leak detection test giving a positive result when the helium detected by the helium detecting equipment inside the vacuum bag exceeds a predetermined second threshold. - the vacuum bag assembly comprising a cured panel, a plurality of uncured stiffening stringers, curing tools (21, 21') for the uncured stiffening stringers with fastening clamps and a vacuum bag arranged directly over the composite part; - the vacuum bag being formed joining individual bags for the uncured stiffening stringers and other bag pieces (25, 26) to cover the whole panel; - creating a local helium atmosphere over the vacuum bag assembly by zones following a programmed zonal sequence for a first leak detection test of each zone (Z j,j); the local helium atmosphere being created inside a chamber placed over each zone (Z j,j); the zones of the vacuum bag assembly to be covered by said chambers are set so that in the direction of the stiffening stringers have a predetermined length and in the direction transverse to them comprise, for each stringer, the space occupied by its individual bag, being a sealing tape of two contiguous individual bags assigned to the zone of one of them so that it can be covered by one chamber; the first leak detection test giving a positive result when the helium detected by the helium detecting equipment inside the vacuum bag exceeds a predetermined first threshold; and - if the first leak detection test gives a positive result in a particular zone (Z j,j), creating a new local helium atmosphere over the zone (Z i,j) for a second leak detection test; the second leak detection test giving a positive result when the helium detected by the helium detecting equipment inside the vacuum bag exceeds a predetermined second threshold.